My experience with AGM hasn't been good.
The bad...
Story #1 - I'm on my third AGM in 10 years in my truck. Not one made it past the 3 year warranty. All three failed the same way, shorted internally. Distributor told me it's a pretty common failure mode as he pointed to the pallet of dead ones behind the counter
Story #2 - A good friend had just put 2-grp. 31 AGM batteries ($600+) on his boat a couple of days before we went fishing. Long story short. Somehow lost his voltage regulation prior to our trip. Took out battery #1. An ACR spared the other, A cooked battery isn't a warranty condition.
The good.... all three where replaced under warranty, no questions asked.
I typically get 4-5 years out of my lead acid batteries. Counting warranty replacement, I get 5-6 years out of the AGM.
IMHO, GM is not a cost effective solution.