there are definately more capable SUV's out there.
The Hummer for one, if you re-designed the 4x4, and strengthened the driveshaft/axleshaft combo, and gave it front and rear ARB air lockers, water proof the bottom half of the cab, install a removable snorkle, and a water tight sunroof, it would beat the MOG i believe. granted Hummer's are slow as hell...
but theoretically, as long as the engine was idling (slightly faster than idle actually) and the intake was forced and above water level, and the truck were water proofed, you could stay underwater for as long as your gas supply would last (you'd also have to run a forced induction for air into the cabin)
for an all-around SUV, i would definately say a 1998 Jeep Grand Cherokee Limited with the 5.9L V8, brushgaurd, and Vegas lights (a-la MattAdams). run dual ARB's and Dana 60's front and rear. Pro Comp Xterrains or BFG MT's or AT's would be decent for still running on-road. about 3 to 4 inches of lift keeps it looking good. full Skidplates underneath, and the Rock slider Nerf Bars (the cool as hell ones that someone on this board makes). you could take it almost anywhere you could get it. granted you have the downfall's of the gasoline engine (i.e. cannot run underwater because a spark is needed to ignite the fuel in the cylinders).
damn, give me a Jeep, a Hummer, AND a Mog, and toss in a 99 Tarus SHO (or maybe one of the old body stylings) and i would be a happy guy. of course i would want my Ranger equiped with an ARB, and there you go.