Pretty much comes down to what terrain you'll be skiing the most. I would recommend getting a big ski designed for off-piste because if you're a good skier you'll be able to ski anything on the groomers, but off-piste is where you really want the right skis. I have K2 Obsethed (179cm, 117mm waist, lots of rocker), they're great for everything off-piste and can rip the groomers too once you get used to them (though you'll have a hard time controlling them on groomers at first if you're not used to wide rockers), so if I was in your place I'd go with something similar to that. Nice and wide to absorb the drops, lots of rocker to float in pow, big and strong enough to charge hard on the steep faces. Some models to consider (not sure if they are all still in production, but if not there will be a successor) would be K2 Annex, Atomic Bent Chetler, Armada JJ, Liberty Helix or Double Helix, Moment Bibby Pro, and Nordica Patron.
That said, I don't ski park, and I doubt you'd want something that big if you are going to be skiing a lot of park. If you're going to be doing a lot of park and a lot of off-piste you'll really want two pairs. But if you're not that serious yet, and just want something that'll be good for everything, go with an all-mountain twin tip, or something between an all-mountain twin tip and a park ski, like the Line Chronic. But keep in mind something like this will not float in pow as well, won't absorb big drops as well, will be hard to ski on the really steep faces/spines, etc, so if you're serious about off-piste you'll definitely want a dedicated off-piste ski.