GAB is a great trinket for snap threat. The sbv it provides is sexy too, if you have spare badges, definitely pick it up, it's very useful and don't let others tell you otherwise. Just know when to swap it out for other trinkets for certain fights.
As for the chest. The glory will give you more threat, hands down, the hit on that far outweights the sbv of the stoic chest plate. You lose some stamina though, and a tiny bit of avoidance for doing that, but I think you're golden with whichever you choose.