I have 33x12.50x15 Goodyear MT/Rs on my FJ40.
They do well on mud and sand, and so far I have not needed to air them down.
They have a bit too large footprint for snow and ice. By that, I think they reduce the weight per square inch a little too much.
I have not done serious rock crawling with them, but they don't slip much, but that may be because I siped the tires.
They do require a lot more steering effort at slow speeds with manual steering. I have really only found this to be an issue when trying to back a short tongued trailer. It's tough to turn the wheel fast enough to compensate for trailer yaw. On gravel and dirt there is no need for power steering from an effort standpoint. (Bump steer is another issue, but that's the kind of steering, and I doubt the size between 1050 and 1250 has much to do with it.)
The biggest objection I have is wheel well clearance. I think 10.50's make a lot more sense with stock wheel wells and up to a 4" lift. They foul the lips. And there is very little clearance with chains. It's bad enough that I'm going to replace my 2.5" lift springs with 4" lift springs, retaining my longer shackles. I think that's better than replacing the tires, which are still almost like new.