[Pdelcast]

I have to agree with Nuz69 as well -- geared for the same speed, the 1518 will run a little more efficiently than the 1515. It will run at lower RPM, which will result in lower magnetic losses. Copper losses will be a wash between the two motors (because current will be very similar.)

In most cases, when geared to give equal speeds, the longer, lower Kv motor will usually be a little more efficient.

This assumes that the two motors have the same winding and construction (like the 1515 and 1518).

Thanx!

Patrick