"Trailer Life has rated the tow weight lower than Cadillac's web site shows which
makes me suspicious who is right or if I'm just not interpreting
things right my self."
These up-scale vehicles are packed with creature-features and technology, all adding weight to the vehicle thus reducing the vehicle's payload.
If I was going to pull a TT, and had a family outside my wife, I would opt for a mega-cab RAM 2500 diesel, Limited if you want all the creature-features. If you are going to pull a decent sized TT, something north of 6,000 pounds, and tow often, you will find the gasser adds driving stress and will struggle at times to keep you moving at freeway speeds. It comes down to what are you going to pull, how far and how often.
I had a Denali, Yukon XL, and it did have AWD with GM's 6L engine. The AWD costs about one mile per gallon but it didn't really matter when I was pulling three tons of boat, the MPG was terrible and head winds made it worse.