inrunner vs outrunner

[alanh]

What are the differences between inrunner and outrunner brushless rc motors and which is the best choice to use?

[MichaelLevy]

Inrunners are smoother hence better sound if you fly an edf, they are more powerful, generally provide higher rpm, but they use up more energy and are heavier. Also a bit more costly.

[Xavier]

For similar watts, the outrunner usually have more torque and less RPM so they could turn larger prop. It maybe due to the larger diameter of the motor itself.
The inrunner are easier to use with gear reduction than outrunner. They could then turn the same prop as the outrunner.