I sold my 2004 Yukon XL with over 311,000 miles to a neighbor and purchased a 2017 Yukon XL SLT from the GM Certified Pre-Owned plan. Car was a Enterprise Fleet rental car. Price was $38K with 42K miles on it. Has only 4WD High on mine. I occasionally move a 8,000 lb boat with mine for a friend. No issues, though I have not attempted to bring the boat up a boat launch after recovery.
I love the vehicle. Quickly got spoiled by the interior upgrade and all the new features I didn't have before. I now have approx 70K miles on the vehicle with no issue. I personally have only had the brake fade issue that was fixed with the GM recall (vacuum pump and associated pipe replacement), but none of the issues on buffeting or other items listed within these pages. Just lucky I guess. I did upgrade the rotors and pads to drilled and slotted ones to maximize stoppage, did AFM delete via tune and changed ALL fluids and plugs at 55,000 for my own mental well being. My family and I LOVE this vehicle and use it for everything from trips up/down East Coast to hauling junk to the dumpster.
I've run both premium and regular in the thing. my mpg ave's 18.5 with mostly town and some freeway. I'll get 20-23 when long distance driving with 3-5 people with luggage and dog in the car. MUCH better than the 2004!
We stayed with the XL version because we've owned both a standard Yukon and the XL and got quickly spoiled with how much more you can haul inside the truck and still be able to use all 3 seats comfortably. The only downside I discovered upon driving the new vehicle home: My garage was 2'' too short to park inside! Do measure before shopping if you have a short garage like mine!
I would gladly do the transaction again if I had to do it over. Best of luck in your decision making process!!