Why is HV better?

[Finnster]

Motor efficiencies also increase with lower kv motors (and thus higher V setups.)

If you are making 2000W on a 4S 90% eff system, you are losing 200W as heat.
If you are making 2000W on an 8S 95% eff system, you are losing 100W as heat. That's 100W more going to the wheels.

Also, the higher turn motors have more TQ, and combined with the eff, can be comfortably geared higher and ran harder w/o danger fo thermals. Couple this with the lower resistive losses, its a far superior system.