How would i know? Well...i sell them. I own a 70cc Pitbull too. I am a seller for Hooper Imports (google it). I picked the pitbull and trail rider because they are copys of something that parts would be no problem getting. I will be totally honest here. The quality isnt honda , yet. what you do get is a good start especially if you plan on using and abusing your machine. The old Hondas are starting to be collected by boomers too so.....If you would want either one of these in a honda youd be paying at least twice to three times as much if you want a really nice example. If there is anybody that wants any motorcycle or scooter Hooper Imports sells and lives around central minnesota (or willing to drive) i will sell it completely assembled with a 6 month parts and labor warrantee for the same price. Long Beach Cycle, Glenwood MN 56334. 320-634-3022. Im a stay at home dad so call at anytime.

Now the showdown.

The 70cc Pitbull is a vast improvement over a Z50 in the power department. In my humble opinion a four stroke 50cc is dangerous on the street. The get up and go just isnt there. The pitbull also has an electric start....very nice. For tough trail riding the pitbull is great. The height and width is an advantage. Fewer branches in the face is good. Would be perfect transportation on a deer path. It has a super low first gear and can crawl up a very steep hill. It will climb as long as there is traction and forward weight distribution. Im 5'10" 165 lbs. I fit great. plenty of room to move, surprisingly. They have a big, if kinda ugly seat that is more comfortable than most large street bikes ive owned. The brakes, for drums, are pretty good. Hard to be great in this department for me since ive owned a few sportbikes with BRAKES! The handling is quick on the street and good on the open road. (40-45 mph comfotably. 50+ in full tuck.) Just keep you hands on both grips when your going good. No waving at pretty girls. The spedo is in mph and the odometer is in kilometers. Why? Dont know. Mileage is around 120 mpg in adverage driving. In sustained speeds on the highway i would think it would get around 150 mpg. You will have to convert kpg to mpg. Take your kgp and multiply it by .64 to get mph.
Improvements: Hooper Imports sells a honda like headlight bucket that is red (not chrome), shorter than the pitbull bucket, and with only one idiot light hole.  Very honda looking and big improvement. Ask for it specificly! Dont mess with sprockets. They are about pefect. Bigger engines are a great improvement to up to a 110cc auto clutch is straight  forward with only minor changes to the exhaust. (I expain on this forum how to put a big engine in a pitbull. Do a search if your interested). I have an ebay bought front end on mine. $365! it came with the forks, tripple clamp, top clamp, front disk, caliper, master cylinder, brake line berings and races. Eazy to instal. I did it mostly for the cool factor. I also mounted a set of original honda fenders. The fenders are a great look. BIG improvement.

The 110cc Trail Rider. Ive had an eazier time selling these do to the engine size and being a little taller. The 110cc electric start is better than the hondas 70cc engine as far as power goes. My opinion is that they handle a little goofy on the street. they fall going into sharp corners (not to the ground). for riding on a trail they are fine. The speedo like the Pitbull is in mph and the odometer is in kilometers too.  Ive had problems with the pressed rims having unacceptable (to me) runout to the point of me having to take them apart and clock the rims to make the rims wobble a little rather than bounce. Every one ive sold has had this problem to some degree. (the pitbulls rims are perfect) I told Larry from Hooper Imports and he half didnt belive me or thought i was exagerating. He said that he never had any complaints before. Maybe my customers and I expect better? there is a fix though...buy a set of used honda rims on ebay. The brakes work fine considering that they are the same brakes that are on a Pitbull. The trail rider is not really pretty in my opinion. It wasnt pretty as a honda either. The only advantages it has over the pitbull is like i said in the begining; height and engine size. 
Improvements: Honda rims if yours arent true. Honda fenders are much better quality. lock tight nuts and bolts on this one. Its not a bad motorcycle for the money. If you dont mind commiting a sin you can pull off the ugly graphics that come with the bike an put on honda stickers or leave it plain.

Verdict. the Pitbull unless you just dont fit on one. You can go on a diet if your fat but i dont recommend cutting your legs off at the knee if your too tall.

If i were Lifan......
I would start with a Pitbull. Drop a 110cc, 125cc or 138cc hand clutch electric start engine. Put on a shorter painted (not chrome) headlight bucket with only one quality looking idiot light (neutral light). The stock idiot lights look crappy. get rid of the annoying blinker beeper. QUALITY steel fenders. They wouldnt have be chromed. Get rid of the silly graphic on the side of the tank that are clear coated over (grrrrrr). Regular fork front with front hydraulic disk break (which they apparently already make). Find a better looking (Stanley style) tail light.
Options: Two paint options; red or in primer. Street tires. Aluminum rim halves. billet Engine dress up trinkets, etc.
I would spend more money in the fit and finish department and sell the motorcycle for around $1600.

Update:
My 138 pitbull is my main vehicle this summer. It has been very reliable.
Alot of people think its a Z50 (kinda is) and really like it. I recently put a regular hydraulic style fork on it and a hydraulic disk brake set up on it. It looks very cool for people who know z50s. The ride is nicer and there is less flex in the front when braking hard. my futre plans are to buy a smaller rear sprocket from CHP. first gear is useless on the street (handy on a trail...) and since i drive it on the street mostly i want to stretch out the top comfortable speed to 45-50. Ill be putting on honda fenders too. I put a pair on a 70 pitbull with a little work and really changes the look (for $120 it should) but for me they are worth it. Honda fenders are like little jewls. 2000 GSXR pegs fit with no mods too! The knobby tires will be replaced with street performace tires. I took of the mx exhaust off and put on an alterd orignal back on. It idles and starts better , has better mid range, and is much quieter. (if you want to do this yourself  ask an i will give instructions on this site) For the money you cant beat getting a big engine, not saying the 70 isnt good enough for the street (the 50cc is too slow for the street and is dangerous in my opinion). If a big engined pit bull is something you might be interested in.....first buy a 50cc pitbull (cheaper and are classified as a motorized bicycle in the title. may matter for licence) or a 70cc (eazier to hook up an engine with an electric start) if you arent handy in recrafting the stock exhaust and figuring out a hand clutch lever and cable (Hooper sells those too) you can buy a 125cc or 110cc engine with and automatic clutch from Hooper Imports. a 110 or 125 will fit with no exhaust mods. Besides an air filter and possible throttle cable everything  just bolts in.
I also bought a 70cc pit bull for an extra motorcycle to have around if the wife a friend wants to drive and for people who want to try one on the road (I sell Lifan too). the electric start is really nice and the gearing is perfect for the road. 40 mph comfortly. up to 50 if your in full tuck and arent too big.
I also bought a x-18 pocket bike with a honda styled 110 engine. Not impressed. the pitbull is much better made. The final drive and rear sprocket dont even line up! Not even close. so if anybody has and likes their x-18... im parting mine out.
when i get my honda fenders and street tires on my pitbull some pics will be posted here.
Do it!

well the panda is doing well and is a fine and very fun commuter. the last time i checked the mileage it was 125mpg. the orignal 50cc engine was getting 157mpg. that is with trail driving and my commute to work which is a long steep climb out of town. the 138 "oil cooled engine" is really ment to be oil cooled in case anybody is wondering. if there isnt an oil cooler or connecting lines mounted to the engine oil feed holes the engines head will starve of oil and melt your head. there is a way around it. i figured since id be driving on the street and usually have good cooling (and no big globs of mud packed in the engine fins) the cooling should be fine without an oil cooler. this is how you do it.
1 drain your oil
2 take off your kick start
3 take out the right side clutch cover bolts
4 using a rubber mallet tap the covers edges to loosen the cover. wiggle it around and pull it off. be carefull not to tear the gasket (there also is a spacer washer on the kick start shaft so be sure to put it back on the shaft when you reassemble it)
5 get a  handdrill and put in a 1/8 drill bit.
6 drill a hole bettween the (exit) oil cooler plug cavity (it is the pressure side of the oil cooler feed that is a part of the right engine case) and the lower right head/cylinder bolt cavity (that headbolt helps secure the cylinder and head down and is also hollow supplying the cam and rockers with oil) in doing this you are bypassing the pressue side of the oil cavity directly into the oil feed head/cylinder bolt.
7 take out the oil cooler feed bolt. spray a solvent of some kind up and down the hole you just drilled to clean out the aluminum shavings you just made. do a good job. blow it out with an airhose if you have one. put the bolt back in.
7 put it back together.

the panda is pretty much like the lifan pitbull. exactly really. wiring is eazy. there are three wires that mach and three didnt. i just looked on the wiring diagram and took the flywheel cover and looked where the mystery wires were going. done. the lights on the bike work tons better too. the bike is registered as a motorized bicycle on the mso. i should be getting the title soon. if some one wants a set up like ive got a lifan dealer would give a good deal to someone buying a 50cc pitbull mx pipe and an engine. probably $1200. keep the orignal 50cc engine or sell on ebay or craigs list for a couple hundred would drop the price to $1000 bucks. quite a deal for a street legal screamer. some people in japan spend over 10 grand on their z50s. i think now a 110 would be a better street choice for an engine. probably last longer. and the stock exhaust with minor modifications would work fine. a good paint job does wonders for the looks and getting rid of the crapy way cheap signal lights. i painted mine a metalic green like my ZRX1200. id like to eventually buy honda chromed steel fenders too.

at the moment i work as a machinest here in town (Glenwood)and after work i take out docks and boat lifts at the local town lake.(Minnewaska) after september ill have more time to get a tax number and have my shop zoned retail. it would be a extra thing to do. they are a lot of fun to ride and simple to work on. (the pitbull and trail anyway). i was thinking of working mostly with those to begin with. if people can put aside the biger is better idea they would find out that there is just right. a trail would be great for ice fishing and taking on dear trails hunting. plus they can be driven anywhere legaly in town too. they arent limmited like a four wheeler or snowmobile. 100mpg+ is pretty nice these days. snowmobiles get around 10. gas isnt getting cheaper. china and india are using more and more every day. supply and demand. I was also interested in SIKK brand of motorcycles. google them if you get the chance. they have a trail bike that is awesome. its half mountain bike and half  dirt bike. they use a honda style engine also.
later.

my 2 cents.
the design is 100 percent honda sound. (on the trail an mini)
the metalurgy, machining and fit are 85 to 90 percent honda.
the fininsh is 75 percent honda.
the price is 70 percent honda (if that).
lifan will continue to improve because its just plain makes business sense to fix the simple problems than to replace whole engines. if people buy from dealers with warrantees the dealers will send back problem engines or whatever back to the company. that cuts into profit for lifan. cant sell junk with a warrantee. not for long anyway.
i think though lifan needs to have better quality control and better finish for americans. spend 10 percent more on that and charge 10 percent more. a better fit and finish will bring in more people than the 10 percent increase in price will drive away. lifan will still be alot less expensive than a big four motorcycle.
ive been looking at some z50 and 90 trail sites and quite a few of the zealots dont like the "copys". mostly because they want to be special and have what is an expensive limited quanity babyboomer toy that is to be looked at, polished and never used. they also think it will cut into the value of their honda orignal. others like the fact they can take a basket case and make something fun and use it like it was intended without having to spend a small fortune.
there are quite afew people that swear by their lifan and have had no problems at all. if a person has no problems with thier lifan isnt that just as good as a honda with no problems?

ps  i own 5 hondas 3 yamahas 1 kawasaki 2suzukis 1lifan engined 138cc z50 "copy"
later