There are a handful of dimensions I think about for towing: Stability (safety), pulling power, cooling, durability, comfort, cost. And it's a matter of solving for all of these based on your personal priorities that results in either happiness or discomfort. I tow a 7500 lb camper with a modified 2012 Yukon XL Denali pushing 450-460 HP & TQ into the driveline, along with all of the attendant cooling challenges that brings with it.
Stability is probably the most subjective, emotionally-laden thing on this list. For every driver who swears by their 3/4 ton truck for towing superiority, there are probably 4 drivers with half tons getting the job done safely. I find my half-ton XL with a well set-up WDH to be plenty stable for me to feel comfortable 100% of the time. That means that I can feel a little pull when being passed by a truck, but I've gotten so used to it after 20K+ towing miles that I don't even think about it any more.
Durability is probably the second most emotionally-laden item on the list. To my knowledge, not one study exists of long-term durability when towing 7000 pounds behind one of these trucks, so all of us are speculating about it. Some folks have replaced their rear axle more than once, while others never have any problems. I believe the AWD of the Denali helps a lot here because both axles are sharing the pulling burden. For those with 6-speeds, the torque converter is the weak link and both the 1500 and 2500 use the same TC. I had mine upgraded to a billet unit with a stronger lockup clutch, so there are cost-effective ways to maximize the durability of the 1500 platform. If I end up having a problem with the rear axle, I can upgrade to a 14-bolt out of a 2WD Escalade, no problem, for about $500.
Pulling power is mostly a function of engine power and final drive ratios. I have the 3.42 axles on mine and they do the job. With the higher output of the 6.2 + cam, pulling power isn't an issue. I can keep up with traffic in just about any situation. That said, 3.73 would be pretty much ideal, and that's a change that can be made for a couple thousand.
Cooling can be an issue on the half-tons, but again, cost-effective mods are available to negate it. I have a fan-forced transmission cooler mounted below the bumper behind the lower grille, and a 2-row Cold Case radiator. I no longer have any cooling problems - even when pulling over the high mountain passes out west.
Comfort is a nod toward the half-tons when they serve double duty as a family hauler when not towing. The mag ride and rear air suspension on the Denalis provides a superior ride - especially when lightly loaded.
Cost is a significant factor. Right now, the cost differential between similarly equipped half-ton and 3/4 ton trucks is 50%-100% with similar age and mileage. But the premium fuel requirement of the 6.2 can eat up that difference over time.
Every now and then I find myself looking at 3/4 ton Suburbans and Yukons, but with the way mine is set up right now, I can't justify spending the additional money. If I were starting over knowing that I'd be pulling a 7500 lb camper, I would shop for a 2500. But I have maybe $4K in parts into the mods I've made so far to my 1500 so I'm still money ahead until the premium fuel tax catches up with me.
