Yes and no. Voltage determines how fast the motors spin, but mAh is part of how the current is determined. If a battery has too low of a discharge rate ©, and a low mAh, it will have too low of current (Amps) to adequately spin up the motors, and can even damage the battery. Motors can draw a LOT of amperage. a set of 180's hit 40+ amps at stall I believe. To determine discharge rate of your battery pack, take the C rating and multiply by the Ah (mAh convetered to Ah, ex: 2000 mAh = 2 Ah) of the battery, this gives you the max amps that the battery can safely output.
Take this battery: http://www.hobbyking..._Lipo_Pack.html 25c * 2.2Ah = 55amps. However, it has a burst rating of 35c, so it's max burst amps is 77amps.
Thanks for the clarification and explanation on that. I had heard how it was related to rev time and drop between shots but this makes more sense now. Still curious as to why the disparity exists with the above data and what I did the other day. Possibly just flywheel build-up but I would be surprised if that alone accounts for a 15-20 fps difference when voltage is even lower than the above data