I have the 99 7.3 in my sig and my wife has a 04 6.0. Even with my tuner on 140 hers will walk off and leave me but in fairness she has an auto and I have 6 gears to run thru. But the 6.0's are quick to be sure. I've towed with both and think mine pulls better but I have my tuner on 80 tow. I get a little better economy city or highway but its not that big of a difference, somewhere between 1 and 2 mpg's. She complains that mine rides like a log wagon and the engine is too loud, the 6.0 is a quieter engine but I like the clatter of a diesel and rarely turn my radio on. If you ask me they are both good engines and it just comes down to a matter of personal choice. Her 6.0 is now blowing coolant out the overflow so I'm gonna hope for studs.