I find 4-strokes respond quicker (the plane in flight) because they produce all their power right away, low in the RPM range compared to a 2C. This helps the plane speed up quickly - almost the same as a large diesel-powered truck's low-end grunt as opposed to a small car's higher top end, but slower 'off the line' punch.

It may not seem important, but one weird thing I find with 4-C's is they also -slow down- quicker. Dunno what to make of this, but it can be useful - maybe something to do with a larger prop? But I'm not sure.

OK. The winner to me is always going to be a 4-C. I don't care what the box your ride came in says - a .60 2C and a .91 4C DO NOT NOT NOT NOT make the same amount of power. TRUST ME. If they -DID- someone explain to my why my lead-sled YS .91 blows my US-60 straight to mars, while my .65 Magnum just kinda tugs it around the sky? I'm propped RIGHT ON for my .65, and probably a little under-propped for the .91. With the 91 i have unlimited vertical, with the .65 I have vertical... sort of.

For your trainer. Go with a 2-stroke (2-strokes and 4-strokes compete evenly when smacked into pavement at 60mph). For your max-velocity race planes - go 2-stroke. For -everything- else there is bound to be a suitable 4-stroke that you'll be happier with over a 2-stroke.