I have owned all three now, all 3/4 tons but not all of them oil burners. IMO the 01 SD 7.3 TD is the best of the bunch. I didnt like the dodges ride, or the fact that the front axle was always in need of some tyoe of repair, weather it be steering brakes or U-Joints. The GMC drove like shit with a heavy load, all though it had the best ride empty. The Ford rides and drives very close to the same loaded or unloaded, and the Power Stroke with a SuperChips programmer alone is no lazy rig.
I havent owned the SD very long yet, only 38k. But so far I have only one complaint, the lack of storage under the rear seat is pathetic, it is huge waste of space. The engineers could have done much better.
But in the end it really just comes down to personal choice.