RPM and rollout question/decision help?

[simplechamp]

So basically if it takes a set amount of power to make a vehicle go it's max speed (e.g. 750W to go 40mph) it comes down to what motor will be most efficient. And from what you are saying the 1850kv motor running at 27k RPM will be higher efficiency than the 2650kv motor at 39k RPM which should translate into the 1850kv running cooler?

It just seemed to me the gearing would kind of even things out. Even if the 2650kv is less efficient, the gearing would be lower, so it wouldn't be working as hard. And even though the 1850kv would be more efficient it would be geared higher, so it would be working harder. I mean, how much efficiency difference are we talking here? a fraction of a percent? 5-10 percent? I have no idea. Is it really enough to make a noticeable difference, or will the difference in gearing cancel it out?