I decided to get a new 1500 last year. At first I looked at the Denali, but the lack of max trailering was a deal breaker. I ended up with a Silverado 1500 LTZ 4x4 short bed with 6.2, multiflex tailgate, tech package, and max trailering. I skipped the sunroof, bed liner and running boards. The payload sticker says 1826 pounds. The truck pulls very well, much better than my 2010 Yukon Denali AWD 6.2 that also had max trailering.
I've crossed the continental divide in Colorado four times so far and I'm very impressed the cooling system. Towing my 7100 pound TT (also a 25 foot AS) from Copper Mountain to the Eisenhower tunnel, my Yukon's tranny temp went from 150 at the Dillon exit to 250 at the tunnel. I did the same trip this year in the SIlverado, the tranny temp went from 136 to 172!
If you do go for the Denali, don't forget the carbonPro bed gives you some extra payload.
By the way, the 837 pound tongue weight quoted by Airstream is not a real-world number. My 25FB's tongue weight fully loaded for a long trip is over 1100 pounds. (I have added four solar panels, a 1000 watt inverter, and replaced the original batteries with a pair of group 27 AGMs; but even without those changes, I'd probably be over 1000 pounds)