I just picked one up and prefer the FHF gear harness over the AGC harness. I really didn't care for shooting with it on, it didn't seem to hold tight enough to me with the AGC bino harness.
Which AGC harness are you looking at? I have one and I've shot trad and compound with it on with no problems. Clearance wise I don't see how there's a difference between the AGC and the FHF. A case that fits a 10x42 bino is gonna be pretty close in size either way, and yes, I've worn both as well as the KUIU harness.