Here's a few turning points in my Denali XL vs Expedition Max limited comparison I went through before deciding on the Ford.
Yukon Denali 6.2L has no low end torque, it needs to rev to over 4,000 rpm before it makes power, so it feels like a turd in comparison to the grunty Ford that has power right off idle.
The Denali has an all steel body so it will rust really well in the northern climate and salt I live it, the ford is Aluminum that doesn't rust.
The Denali is STILLLLLLL running a solid rear axle rear suspension which is technology from the 1960's, whereas the Ford is running an independent rear suspension so it rides far superior.
The Denali is getting re-designed for next year or the year after, so if you buy a new one now, yours will soon be the old one, whereas the Ford is completely redesigned freshly last year.
The 3rd row seating the in the Ford comfortably seats adults and the 3rd row seat in the Denali XL can barely fit a young child in the seats comfortably. Horrible 3rd row in the GM's.
Thats all I needed. I bought my 302A Limited for $16K under list, so I think it was a no brainer to go new when the used ones were selling for close to that at the time!
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Thats my thoughts.........