I've spent the last few days off from school out at the field experimenting with my Extreme Flight Extra EXP with regards to using a three cell LiPo vs. using a four cell LiPo. The 4S battery provides the Torque motor with way more power than with the 3S, but makes you use a smaller diameter prop for amp and load reasons. The EXP's are "bigger" planes than the planes I'm used to flying because of the EXP (Experimental Progressive) design and the amount of extra surface area this plane has regardless of the wingspan. Because of this increased drag, regardless of the plane's physical size and weight, you need more power than you normally would on a plane of similar size.
Today I came to the conclusion of using 4S in my EXP because with 3S there just wasn't enough power to pull out of botched maneuvers in any sort of wind, and also didn't have enough verticle punch out of a hover for my taste. Even though the 4S battery requires a smaller diameter propeller, the huge authoritative surfaces of the EXP design provide enough control surface area to make up for the reduced vectored thrust. Sure, in a hover it's harder to counter torque, but it's all about adapting to this new design of planes, and that is what I intend to do.
Here's the video from today of my EXP on 4S. Enjoy!