Re: 2 vs. 4 Stroke...
My opinion is that the way things stand taking into consideration what's available in the marketplace now a 2 stroke is the better option for powering a bicycle.
Mainly, the 4 stroke kits available don't look as pleasing as the 2 strokes and they cost quite a bit more. But if someone started selling a 4 stroke that looked more like the old Ducati Cucciolo moped engines (see pics) with nice exposed rockers for a relatively reasonable price I think the situation would change drastically. Suddenly the easthetic would split in favor of the 4 stroke in my opinion.
As for power I say it all depends on gearing more than anything. 4 strokes typically have more torque on the lower end and a broader power curve whereas the 2 strokes have a narrower power band that peaks at a higher rpm. That's why you can't simply release the clutch from standstill on your 2 stroker and get going: not enough torque with just the single speed.
As for a 2 stroke being better because it has less moving parts it's like saying that in a fight you'd pick a wooden club over a handgun because the club has less moving parts. The HT 2 strokers available are quite troublesome/finnicky enough (mainly because of poor materials and manufacturing)for only about half the moving parts of a 4 stroke.
McGyver could fix that with bubble gum.