Talking about the Mini C. The Rio is much bigger, so for that you would need a slightly bigger motor.
A higher mAh will make you and the ESC happier... you for longer runtimes, the ESC because you have more power reserve.
Just an example: on a 600mm mono, I have a Feigao 14S (46A), with a 60A ESC and a 3S 4200 20C battery... and they lived happily ever after...