What are major differences between Denali and LTZ in 2015i besides Engine/Trans?

[Tommytuna]

Very true. I think the 5.3 is plenty for us. Given we are coming from a mini van / Toyota Highlander (and my other car is a Volt) the 5.3 is more power than we're used to. Fuel economy is very important to us and I think the 5.3 fits the bill nicely.

Just read that they recommend premium fuel in the bigger engine vs. regular in the 5.3. That just about seals the deal for me on the 5.3.