I was in this quandary as well. Once you option a SLT reasonably you can buy the Denali with no options, get much more as standard features, and only end up paying well less than ten percent more. I do think a stripper Denali will hold it's cost differential at trade or resale as long as it's a 2015i.
I wanted the 8 speed so the decision for me to spend a little more to get it wasn't that difficult. I'm still waiting for mine to be built - supposedly week of 6/8 and still was able to keep the sticker under 70K.
---------- Post added at 08:49 PM ---------- Previous post was at 08:45 PM ----------
I forgot to mention the fact that the I liked the fact that with the 8 speed you do get the towing package thrown in along with two speed transfer case (got the 4WD) and 3.23 rear end.
Add my to this list---what to do?!? I don't want to be that person that buys a 15/16 with the 5.3 6-speed, and then they do a 5.3 8-speed the following year.