37" BFG AT's or 35" Toyo MT's
I really loved the stock tires but wore out to quickly for me. I am most concerned about mileage and snow.
The stock tires use a softer compound than the 37's so wear wont be an issue. As for snow/ice I'd stick with the BFG's. Most MT's are terrible on ice, hard pack etc... They do well in the deep snow though.