A Sequoia probably has a slight performance and reliability advantage, but GM has closed the quality gap to the point where it may make no matter in a purchase decision.
What is left is that the Sequoia had a poor interior design on the day it was released. That was in 2008, and car interiors and technology have advanced profoundly since then. At this point, it's a utilitarian nightmare of hard, grey plastic. It is in drastic need of a redesign - I'm sure it will be very competitive once they get around to that, but not until.
As for the Denali versus the SLT - I carry that thought around also, but I have little experience driving either. Objectively it's an engine and transmission difference, plus slightly nicer wood trim inside and perhaps a couple of electronic baubles. It's a rather sharp price increase.
How big a deal are the magnet shocks? Also, how expensive will they be to replace at 60,000 miles?