I don't really know about that. maybe, problem is the rims being narrow kinda limit the larger sizes you would run on toyota split rim. I mean how many different size tires or what tire would you run on it that you can't get in a 15?
For me it is the selection of 30-32 inch narrow tires you can run. I'm a fan of keepimg the tires inside the fenders. Yet I don't want to run the 33x9.5 BFG's. I've run through a couple of sets of the BFG All Terrains now in the standard 15 inch size, and I have been disapointed with the life of the tire. They have all developed bulges in the tread as they near the end of their life. I want to run a 235/85R16 to gain some additional tire size, yet retain stock suspension and closer to stock performance. But I will also get a load range E tire, and a better selection of all terrian tire treads. What I really want to run is a Dunlop Radial Rover RT, good commercial grade all terrain. Better yet would be a Toyo M-55, but they are pricey. Currently running them on our Ford F-250's at the surface coal mine I work at. They are the best tires we have ever run out here. And I have tested them thuroughly in all conditions, that type of tread is quite impressive.
Of course, I haven't run the Dunlops yet, but that is the tire I want to get, as the 40 needs new tires. So this is all speculation, but for my wheeling and use, this is the route I want to go.