Neu motors are probably the best thing you could get. The only rivals I can think of are Plettenberg, Lehner, and maybe Kotronik. (I'm sure I spelled those wrong. Here is a video of a Neu in a Vendetta ST, and this isn't by far the fastet/biggest Neu motor you can get.
I think I should mention this is on 2s.
http://www.youtube.com/watch?v=0iZuUoax6O8&feature=user

I don't know why, but that reminds me to add medusa to the list.

Mamba motors are pretty fast, don't get me wrong, but they have almost no torque. They are very popular because the Mamba 25 combo was, and is one of the cheapest brushless systems you can get. It was one of the first mass-market brushless systems too. Until about a year ago they practically had a monopoly with 1/18th scale brushless systems. These motors are very fast, but you can't gear them very high at all. Mamba motors really aren't that good once you think about it.

I changed a lot of the motor information too. Shorter and sweeter now.