Marco ... it would depend on what purpose. High KV means it will draw a lot of amps for the same number of cells when compared with a lower KV motor of the same size. So the question is what sort of plane or application. You must factor in the load, which is your prop. Let's assume we have say a little pylon plane. High KV is needed as they wanna turn small props at high RPMs. The high KV motor will not want to run a say 7" prop when the optimum is say a mere 5". High load will cause your motor to burn. When you fly say a glider, you want low KV motors so you can turn a big prop for the thrust, speed is not the main issue here. So what is your application and what is the motor size?