RE: Mamba Competition 1/18 any good?
You'll see an improvement in speed simply from the Kv bump. The 1/18th size hackers have Kv ranges from 3900-4700. the mamba comp. motor is rated at 6800kv.
Not to say that the mamba comp is a "better" motor... if you compared equal kv hacker/e-flite motors vs mamba motors, they'd be quite similar in efficiency and amp draw.
You'll see more of a jump if you got a 3-cell lipo, and kept the hacker.