Plenty of opinions and threads on gas vs diesel. I read all I could and went out and bought an older diesel, we're very, very happy with it. I didn't think an ISB would work for us so the minimum I considered was the ISC 8.3, we start out at 7200' and mostly go up from there.
I tow a built Wrangler on a trailer (~6500bs +-) when I head out alone and we tow a mild Cherokee (~4000lbs) when we're out together. We converse at normal levels while climbing the steepest of slopes and the air bag ride (another benefit of most diesels) is very nice.
Do your research and make the decision that's right for you. The newer V-10s do have some good horsepower/torque but the TQ is not anywhere near what the diesels put out (cue the "horsepower gets you up the hills folks) and there are other significant differences in cargo carrying capacities, ride, towing capacity etc. There are also some upsides to the gas units, such as operating cost and initial cost.
Good luck in your hunt.
Dave