Speed is a function of kV and gearing so an 1100kV motor is always going to be slower than a 1275kV motor given the same gearing and same voltage. The 1100kV can is bigger in diameter but its a lot shorter than the stock motor. The overall volume of the two motors is pretty similar although the...
Personally I get the 1100kV motor. The stock motor is a 1275kV motor. Youd have to gear up to a huge pinion to even get close to the stock speeds so for me it would be the 1100kV.