low end motors vs high end motors

I'm very interested in this question too...I've been running Low end motors and I also am considering the switch. Nearest I can tell you get two things, lower temps and better efficiency. My question is how much for both of these...mainly how much more run time. Do they give 5% more run time? 10%? 20%?

About the only thing I'm not happy about with my low end motors is that with 4900Mah batteries I can only make 15 mins if I really drive slow. If I get on it I often times will only see about 13 mins which is often times just a little too low.

DM