If You are flying around doing only right turns in a confined space, or the '0' talent manuever of spinning it quickly around and around to impress someone who doesn't fly, I could see how one motor could run a little hotter, other than that, I don't think it should be significant.

That got Me thinking; that may be another slight benefit of having a heatsink; as it may equilibrium or temper a motor running a little hotter than the other since they are sharing the heatsink, but I'm not sure on that.