We had a Yukon Denali for a weekend. My wife opened the back door and laughed at the cargo space. Can't even put groceries there. Plus the third row is a penalty box for anyone out of a child seat. Meanwhile, the long wheelbase has both more 3rd row space and 3'x4' floor space with the third row in use. When we shopped, the long wheelbase version costs about 5% more. The only reason I feel to buy the short wheelbase is the long doesn't fit in a garage or you only have a family of 4. However...
Towing 7500-ish pound loaded TT with 5+ people in the SUV is tough criteria for any half ton. Payloads are in the 1200-1600 pound range. 7500 pound TT means 1000 pounds of TW. Does the family and anything else to occupy their time while traveling only weight 200-600 pounds? As you said, not one wants to make a $65k mistake. Great that are doing this research now instead of after the RV or TV are already purchased. Check the tire and loading stickers when you open the driver's doors as you shop. Note what they have where mine says 2051. That's why we have the 3/4 ton. There are still some new 2013s available across the country and you should find fairly loaded ones for under $50k compared to $60k.
