Please help noobie on Motor/Battery selection for E-Revo

[SypderFungus]

SuicideNeil, up in post #3 you said that the 1600kv Medusa is a little slow for 5s. When i put it in BrianG's calculator I get 29600RPM. The other combination that is getting a lot of recommendations is the 9XL on 4s which works out to 27400RPM.
The calculator shows the Medusa having 1 more mph over the 9XL.

Can you help me understand your statement?
Is it a torque thing? Is it becuz the Medusas are rated at 60k RPM?
If i bump up to 6s on the Medusa I get 35500RPM. Wont that cause a lot more heat or is that going to be more efficient?

Does anyone know the optimum RPM for Medusa V2's?

Thanks