I've had the BFG AT K/Os. Good tires, wear very well and roll very well. The 3-ply side wall is a plus. I opted to trade mine off because they didn't provide much traction (IMHO) in very light mud and so I picked up a set of Mastercraft Courser C/Ts, which I like better than any tire I have owned to date. I would describe the C/Ts as an in-between tire of an AT and a MT. They roll great, wear great, their lugs are siped and they do well on wet roads, puddles, and the mud that gave my BFGs grief. I'm waiting to see how they do in the snow. I didn't care for the Courser AT IIs, but the C/Ts are a great tire.
Size wise, 235s will fit under the fenders on stock (5.5") rims... so that's the size I would recommend.
All of the above is contingent upon what YOU want and what you use your truck for. After that... it's personal preference.