Ive skied them both and am currently on the ARV86 because I prefer a narrow ski for park... that said I got to test the poacher pre release a few years back and have been in love with it ever since.
The poachers have a much tighter turning radius than any other park ski on the market (from major brands... next year the new chronic will have the same radius) and unlike their predecessor the Shreditor 92 this makes their stiffer core really come to life. If you're looking for a ski that can carve groomers as well as have incredible pop off jumps look no further. The cons with the poacher is that its full sidewall and pretty damn heavy particularly in terms of swing weight, Ive also had about 5 or 6 customers at the shop this year lose the rivets in the top of the ski, luckily K2 has a pretty bomber warranty and gave me more rivets which as fixed the problem for everyone except one customer who skied them a few days without the rivets and they delaminated. IMO if you are someone who is into park but also likes to rip all mountain this is one of, if not the best ski in this category produced by one of the major ski brands.
The ARV 96 is going to be a much more traditional park ski in terms of turning radius meaning it likes to go fast and straight but is not going to carve it up if you like to ski short radius slalom style turns. The 96 has a pretty nice flex pattern however I have found that they softened up after  about 10 days riding and became quite noodlely for me which works out quite well for you new wavers looking to butter all over the mountain. They hold their flex pretty well underfoot and after a full season I find them still solid for catching icy landings. If you're looking for a wider ski thats soft in the pow but can hold its weight in the park and are worried about swing weight on the poachers then the ARV 96 is for you. + Bonus next year they have the same "tapered" sidewalls that some atomic skis have going with full height sidewall underfoot and then like a 1/2 height sidewall going 3/4 up the tip and tail of the ski, this should address the flex issues and torsional stiffness issues I found while riding them.