don't get me wrong, a properly setup banshee would handle tighter trails with ease, but a woods/tight trails shee isn't going to make 60+hp, because your building it for torque and that's not really it's forte. if your building a higher hp banshee for speed, it's going to be a lot peakier which leads me back to my question... what kind of riding does he want to be "faster" at.
I mildly setup yfz will be pretty damned fast and will hang with quite a few banshee's quite honestly. It's not that hard to get 54hp out of a yfz, where a banshee would generally need some good pipe, portwork, timing and so on to get the same hp.