So, not exactly your scenario, but here is my experience. I upgraded from an 03 2500 8.1 Burb to a 2011 Yukon Denali XL. I use it to tow my 6500 pound boat.
From boating forums, I know many people who sing the praises of the XL and Escalade for towing. But my experience has not been as good. To me, the towing experience is below expectations. At 65 MPH it is simply OK. Any faster than that (think about passing a slower moving vehicle on a 2-lane road), and I get quite a bit of trailer sway, and it works its way up to the Yukon. I know my problem is not my boat trailer as it towed fine with the older Burb as well as my truck in signature.
I hope my problem is the P rated tires, and will likely upgrade this year. But I am not holding my breath either.