I run 5 cells with a 5.5 LRP Brushless indoors and really like the feel of the car plus it gives me more options of where to put the weight in the car.
Most people here reckon it's easier to drive brushless smoother with the one cell less and have no speed problems down the straight against other guys running 6 cells.
Going to be running an old BJ4 outdoors and the balance is really good with 5 cells too.
I really like buying 5 packs and making 6 out of them too