[glassdoctor]

The 540 and 540c are the same motors... except for the case design. The c has the cooling fins.

Some prefer the regular smooth cans used with a separate heatsink. I like the 540c finned can.

Either one will do fine. For an emaxx you might want the smooth can just because the smaller diameter will allow more room for gearing options. Big can motors hit the tranny in the emaxx, limiting gearing options (or you can shave down the fins if needed)