This post is getting a bit old now but it seems relevant to share my experiences. Here in the mountain in Australia I have 4 really distinct seasons with dry dust/loose gravel/heavy rain/mud/snow etc
I'm now on my 8th Range Rover, including one P38 like yours. Tyre experiences have been as follows:
Michellin snow & mud - never again. Baggy side walls and soft compound totally unsuitable to off-road driving causing multiple punctures
Cooper A/Ts - Very average quality, poor wet handling. overpriced
Pirelli Scorpion - never again. Went "out of roundf" soon after fitting, dealer and importer largely unhelpful
Bridgestone Duellers - not good in the wet, to the point of being dangerous
BF Goodrich A/T KO - excellent all round, quiet, good grip in all conditions
BF Goodrich A/T KO2 - the latest series. Even better than the older KO series with the tread wrapped around the shoulder. I cannot praise these too highly - not cheap but worth every cent
Kenda Klevas - were already fitted to a 93 Classic I have just purchased. Did not expect much but am pleasantly surprised at the handling and quietness both on the gravel and on bitumen - the latter included extreme wet weather. Have to say I do not think they are as good s the BFGs but at a saving of $100 or more per tyre, they are great value
We buy about five sets of the AT K/O's for our shop trucks every year. have them on all three of my trucks as well. Best all-purpose tire available and worth whatever they cost. They wear like iron and do very well in wet and slop. Anything worse than that and it becomes a function of tread aggressiveness and compound. There are better tires for when things get really bad, but they're louder than hell and you can watch them wear.
The AT needs to be rotated regularly. They all do, but this tire is less forgiving.
I bought a truck a couple years ago that had Bridgestone Revo's on it. They were super quiet. I didn't keep it long so I can't tell you about wear.