I think where you live in Western NY, the interiors hold up better in general. Down here the frames never rust but the sun beats everything all to heck eventually. The pics in the OP are the perfect embodiment. The paint and the interior look great. The underside, not so much. Here, it is like the exact inverse of that. It's super important to garage your vehicle here if you want to it to stay looking nice.Did you drive a 99-02? Or just a truck? 03+ had a refreshed interior and SUV GMs were usually better equipped. When I think of 3V Fords, I can imagine them as sparse as you're mentioning with the GM if I think of an F-150. But if I think about a SUV, I can imagine them well equipped. Also, with comparing to a Navigator you'd have to compare to Escalade.
I'm probably biased but I find the seats some of the most comfortable, controls well laid out, enjoy the interior styling and amenities. I have heated seats so I'm content. Perhaps some of the charm to me is the dated interior. Remembering a time when things were different. The simplicity and ease.
Something built by General Motors Corporation and not General Motors, LLC.
Probably the Pacific NW and Northern California are some the better places with the best of both worlds, not so much rust but the sun not beating everything up either. You will tend to get rock chips if you drive in the mountains though.