Robot Build: 12v DC motor at 11.1v 3S or 6v motors at 7.4 2S

In general, it is better to design a system using 12v motors being driven by 3S lipo batteries (under volting a little at max power) or 6v motors using 2S lipo, potentially over volting a bit at max power?

With the higher voltage, you get lower currents for the same power, which is generally a good thing. Current makes electronics get warm…

Thanks. Good point.

Given that Pololu sells 6v motors and the nearest battery is a 2S (7.4v) are people using 6v motor generally stepping down the voltage or limiting it (by say, not running the motor controller as full speed)?

Or do people just not worry about it on hobby robots? (e.g. “It doesn’t really matter much for hobby projects, but for something more industrial, over volting would become a bigger issue.”)

I haven’t built any robot yet, but lots of other RC controlled stuff. Generally, small DC Motors have no problem with voltage somewhat higher or lower than rated. Even 50% or more are ok, as long as you keep an eye on the amps. Generally, you should never exceed half the rated stall current during normal operation. For prolonged periods, 25% of stall current or less is what you should aim for, because there you get decent efficiency and not too much heat.
However, with 7.4 instead of 6 V I wouldn’t worry about anything.