[RC-Monster Mike]

As a general rule, as the motors pole count goes up, the "efficiency window" gets smaller. Most out runners have high pole counts, which means there "sweet spot" for ideal operation is significantly smaller than the 2pole and 4 pole motors typically used. They are great in aircraft - high torque and a much lower degree of varying power. Cars/trucks are usually run throughout a wider and more variable range of throttle input, so they are best served with a wide efficiency window. A good outrunner is quite efficient when used in its intended range.