Do you drive the Denali up and over many mountain passes? Planning to take mine to Colorado this summer and a bit concerned about not having the low range transfer case available.
I lived in Colorado for 10 years, and did quite a bit of offroading. Are you trail riding west of Denver, or are you doing something like the Alpine Loop?
If you're going to be just riding trails, and not doing hardcore stuff, then you should be fine.
One of the biggest benefits of the two-speed transfer case is descending steep grades. It allows you to use the brakes sparingly. If you're going to attack Engineer Pass, for example, you better plan extra stops on the descent to let your brakes cool.
It's one thing descending a steep 50- or 100-foot hill. Sure, you can do it entirely with your brakes. But long, steep grades going down hundreds or even a few thousand feet in elevation? That's a lot of potential energy that needs to be absorbed. I had a 5-speed manual and the 2-speed transfer case. I had 10 gear ratios to choose from and could pick the gear that allowed me to descend without touching either pedal.
Additionally, I've never been a fan of the half-ton braking systems on GM trucks. I they're under-braked and prone to premature wear/failure. So stressing it out on long steep grades could be problematic.