ORIGINAL: Rodney
Far more important than the capacity of the battery is the quality of the switch and wiring, especially when using any of the 2.4GHz systems. It the wiring between the battery and the receiver has any appreciable impedance, when you draw that momentary rush of current by commanding any high draw servos you will get a voltage drop in that wiring. If it causes the voltage at the receiver bus to drop below the reset (reboot) level, you will get a temporary loss of control. This will happen whether you have a 4.8 or 6 volt battery.
This is very true, I have had one battery short out and two switches go bad, one with a wire short and one with a bunch of dirt get between the poles. Checking voltage with a good loaded meter between flights is a good idea, a lot of people use the volt watch. I do both. I started using a fast field charger some years ago, not always needed but if my batteries run low on a long day I'm not grounded. It's a great tool, I used to fly a lot of giant scale events and be at the field for days on end and the quick charger kept me flying.