Higher voltage and efficiency

[Shonen]

the 'efficiency' claim for HV is not necessarily for the motors, but the batteries and wire which have more or less fixed resistance characteristics. Like everyone said, the heat losses goes up quadratically with current, and by going with higher voltage for a given wattage it reduces both current draw and heat.

To be truly scientific, the equivalent watt-hour batteries and different motors (with similar total RPM) should be put in the same chassis. Castle's CMS36-4600 on 3s 2650mAh and the CMS-6900 on 2s 4000mAH seems to be a good matchup for ground RC.