P. I've wheeled my Liberty very hard with P rated tires and have never cut one. I don't think an extra 10 pounds per tire (and it's rotational mass so it's an even worse impact) is worth it. A lot of extra strain on everything. Double check to make sure the weight difference is big, but that's what I found out when looking at P245/70/17s vs LT 245/70/17s in Load Range E. Load range C or D would be lighter, could look at those. But, I'd really think carefully. Many people wheel with P tires and do ok. Most AT tires even in P ratings have thicker sidewalls than a standard P tire.
15 KL Limited V6 4x4- Granite Crystal Met. on Black/Lt Frost beige
07 LR3 SE V8
05 KJ Limited: Lifts, bigger tires, skids, rock rails, Warn M8000 winch etc
96 XJ Country