Add me to the pile that say both provices (+PEI if you so desire)

I haven't been to Newfoundland so I'll stick to what I know: Nova Scotia. You can do Halifax and area (Peggy's Cove) for a couple of days and a loop up to Cape Breton for another 2 or 3 days. Newfoundland is bigger so I'd budget a couple of extra days for more exploring there.

If you still want to stick to one province I'd suggest Newfoundland only because you mention you want the wilderness and with its size and better chance at seeing some giant moose it would (just) edge out Nova Scotia.