The best trike IMHO is the current Pashley Tri-1 Seven speed. And I'll tell you for why. It's head and shoulders above any of the offerings from Jorvik and Mission. *Everything* about a Tri-1 is better, the design, materials, construction and components. It's a thoroughly resolved product which is made to much higher production standards than any of the budget Far East trikes. The only machines which might give the Pashley a run for its money are the few offerings from the Dutch and Germans, which are invariably more expensive (even before you factor in the cost of bringing one in). When I sold trikes and other pedal powered things for people with special needs the Pashley Tri-1 was far and away my favourite product. It's such a complete package - there are just two things that I would change about it: 1. It comes with a chromed steel seatpost. It really deserves an aluminium post. 2. The 10 week production lead time.
Re: Small wheels. Bikes lean into corners, which means that all the (gravity, bump forces and cornering) loads run straight down the bike through the wheels. The side loads are negligible. Trikes on the other hand don't lean in corners, so the wheels must be built strong enough to resist cornering loads. Small wheels are stronger. There are more spokes per inch of rim circumference. The spokes are at a more acute angle to better resist the forces imposed on them. They flex less than tall wheels under load, so they even handle better in corners. And (all other things being equal) the difference in efficiency (rolling resistance) between 20" tyres and 24" or 26" tyres is so minimal as to be undetectable from the saddle.
They retail for £800 (last time I looked). The going rate for good well used example off
ebay is around £275 > £375. A mint one should sell for around £500.
If looking at a used folder check that the hinge closes securely. If a muppet has ridden it without fully tightening the folding mechanism it can bend the frame seriously enough to write it off.