I've got both, the skate banana isn't really all mountain at all - more of a fun, forgiving jib stick. IMHO great to learn on and some people I know seem happy on them at speed, but they do chatter. Maybe the attack banana or TRS is worth looking into? Or the riders choice if you want a better base. Attack banana is mellow mag though. Personally if I ever replace mine it will be with a Slash - Happy Place.
Proto is a park board that's pretty versatile and happy anywhere. The camber sections make it feel better on edge than the skate banana, and it is a little more effort for jibs, but not difficult. Doesn't suffer cosmetic damage too easily cos of that nice topsheet. Sintered base is great and their side cut grips just fine. It's a top notch bit of kit, and is really popular nowadays.
I'd say proto all the way. There are more all mountain focus boards in the NS lineup though