A stiff ski will handle better. It will turn like it is on rails, and be harder to break loose. This is great if you can control it, but it can get you into trouble sometimes. If you come down on a switch landing with your weight thrown off a bit, you may get "stuck" on edge trying to slide around but the ski just wants to keep railing. In this situation a softer, more forgiving, ski would help because it will be easier to slide back around and man-handle if you get into a sticky situation.
But stiff skis are TONS of pop. Also, they can hit bigger jumps much easier than a softer ski. A stiff ski will still land solidly and ride away from a big jump without a perfect landing, where a softer ski may get a little squirly if you get off balance.
They both have benifits and downsides. The best way is to try them. You may even have different ski tastes one year to the next.
Skis with butter zones will handle like crap. Unless you spend 99% of you time buttering and your edits are only filled with shots of you buttering, I would stay away from butter zone skis. The 2 seconds of easier buttering you may get during the day is not worth suffering for the rest of the time on the mountain.