My Z66 Avalanche is the best truck I have ever owned, and I have had several over the years. I added a Gibson exhaust, K&N air filter and the computer adjustments. The truck runs awesome. The only problem I have had in 28,000 miles is the steering shaft, since it was replaced, nothing, not even brakes. It tows my trailer with two big bikes in it like nothing is even there. I recently added 20" wheels and I get lots of comments on the "green monster." The truck is comfortable for five adults and the ride is more like a car than a truck, very smooth. I use the fold down feature often, mostly leaving the rear window in place and folding the lower section (for ladders etc.). Excellent!!!
Drivers compartment is the best of any truck we looked at. My wife said the back seat has the most comfortable lean angle and leg room of all the trucks we looked at. I love the steering wheel mounted radio controls and the cruise control is right at your fingertips. Dependability is great!!
The larger, wider wheels I put on help the body sway around corners, I don't know if stiffer shocks might help, but may spoil the car like ride. Tough choice. Overall, the best vehicle I have ever owned.