C4 hands down. its actually uncontrolable in my opionion. as far as gearing in most minis and micros you can not change the gearing I will be getting my mini t to about 36mph with mamba 8000 quart 33A and stock 6 sell losi pack. If your going with either motor c4 of mamba(less likely to break, More well known people for bl motors) Get the quark 33 a it is the best system and check out these combos
www.b-p-p.com