Andy,
Hands down, I’d go with PanZoom. It just seems easier, faster, more controls, but the number one reason is that you don’t leave FCP’s workspace. Stagetools forces the extra step of having to go into another interface. Number two, and this is HUGE, a PanZoom clip’s duration can change, and the effect moves with it. If you want to change the duration of an ST clip, you have to go back into the damn interface and re-do it.