Not sure yet. Same as you guys 31.7 with the BFGs or 32.1...
Don't really wanna do too much trimming. 265/65 doesn't require any lift or trimming... Easy route. I kinda like that. However there's much more choice if I go with 275/65...
There are definitely more choices if you go with 275/65R18. I chose 265/65R18 because I did not necessarily want to keep my truck lifted full time and I did not want to modify the wheel wells. I do like the look of the extra height, but with my roof rack and the supplies on top, it just did not seem like a good idea. When I go off roading I lift to off road mode and then use my IIDTool to get a bit of extra height as needed.
For me, the capability of sticking with the 265/65R18 is far beyond what I need, so I did not want to go too crazy since this is my daily driver. I am extremely happy with my decision and the BFGs performed amazing off road last week.
Keep us posted!