Personally I would go the 285's. In my opinion the slight higher clearance will help especially if your in ruts etc etc. Last thing you want it to be dragging the diff centre on the centre of a rutted track. Thats a show stopper every time. I get it on the rear diff even with 315's as my rear diff is the larger H260 diff. Kinda wish it wasn't for this reason.
On the highway your fuel eco should be better with the larger tyre, more speed for less revs, but it will be opposite when in low range or slow stuff. But the difference either way would equate to sweet fa.

Your usage is rocks, sand, mud, hills etc. So to me the 285 is a no brainer. That little extra clearance over the 265 will help. Each to their own though.