hmmm...im not too sure if pronating or supinating the wrists will have an actual effect on the press itself, but if it helps someone control the target muscle better, go for it. since these are all compound movements we each have our goal as to the muscle we are targeting. if its the chest, then use whatever grip allows you to contract through that movement with the target muscle under control. if its the tris, etc.
i feel this is more of an individual thing.