The new cummins has over 800 pounds of torque. Not sure about the new isuzu. Cummins used to be the most obnoxiously loud one of the litter, but now they are almost silent.
Don't know what to tell ya Randy. I think you have a tough decision. I'm a GM guy, but I have to say that I do not like the 9000 series GM trucks. They are not put together as well as the pre 07's. You ought to just go spend some wheel time in each. Sometimes the creature comforts of each can be deal breakers / makers.
I just paid $115 for an oil change in the vette.