9xl, 5s, Quark 125b + Lipo battery holders?

[MTBikerTim]

If I run 6s will this keep the motor cooler if I get a motor with the same top rpm? eg:

5s on 9xl is max unloaded rpm 30839
6s on 11xl is max unloaded rpm 30303
so they are very similar rpm will the 6s setup run cooler under the same conditions then the 5s? I'm thinking that I might as well go 6s if it will be better as the compro esc sounds like it can handle it, no worries.