I don't see the point in a Denali vs SLT without the 6.2L and AWD standard. Hell, give me an SLE with bucket seats, dual climate, and a 6.2 and I wouldn't even bother with the SLT.
Just put 5100s on my double cab all terrain. All stock suspension and left it at the lowest setting on the front (no raise). Feels a little softer in the corners but a huge difference when it comes to damping over multiple bumps.