[pasan]

I would select the 2000kv for running on 6S. You'd still be within the operational limits of the motor, and I find that Medusas' sweet spot is between 35k and 45k rpm, at least thats when my 36-50-3300 really becomes lively. Also, when you're running 6S the current draw is less and as a result everything runs cooler anyway, same reason why you see a difference between 5S and 4S too; if you're pulling the same amount of wattage from both setups, the 5S setup will obviously have a lower current.