Hi KK, HobbyKing have a huge selection of motors, and some of them are very very cheap! As for whats more powerful, I think I'm right in saying the KV = revolutions per volt, so the 800KV on 11.1V lipo will turn at 8800 RPM, whereas the 1400KV on 11.1V will give you 15,540 RPM. However there is more to it than that, ie torque, and I've only ever found 1 website that explained it well, but I was at work and can't remember where it was! If I find it again I'll email you the link.