New to brushless-which mamba?

Hi, like stated I am new to the world of brushless and was just wondering which of the mamba packages do you think would be the best for a stampede and a T3. I was thinking about the 5700kv. I would mostly want it for bashing and beating nitros but would like some custom aspects in case I want to race the T3. One other thing, why is the mamba package cheap compared to others, there package-motor and controller are sometimes less than some controllers; is it because they aren't as good as the others? Does anyone have any better combinations (motor-controller) they think are better? Thanks.