[lincpimp]

People who are geared for 25mph might be...

Not sure what kind of info you are looking for, but higher voltage is always better. Lower voltage will demand the use of a very efficient motor, such as a neu, to perform and not kill batteries. You still need the same amount of power to get those truggy tires turning and move the weight of the vehicle, regardless of how much or little voltage you run.

So you will need the same physical weight battery, regardless or voltage to get the same runtime and power. So either a 3s 10000mah, or a 6s 5000mah, for example.

You will need to run the same size motor for any given voltage, for example you want motor rpm around 35k rpm, and want to move a 10lb truggy. A neu 1515 is a tried and tested motor that can get the job done. You would need a 1600kv motor for 6s, or a 3200kv motor for 3s. A 3200kv motor in a 10lb truggy geared for 40mph on 3s lipo will be pulling some amps, I bet 250 or more spikes, and well over 100 average. Stuff gets hot at that level, esc, motor, wires, plugs, etc. Plus you need a good battery to handle the load.

Higher voltage is just better all ways round. Now that we have the MMM, an inexpensive esc capable of 6s, there is no reason to not run 5-6s in the heavier vehicle. It just makes more sense. Going even higher in voltage would be better, I would prefer to run 8s, 10s or 12s. My varied experiments with 8s and higher have been very positive, especially on heavier vehicles and higher gearing.