I’ve had FHF, AGC, and have a Marsupial.
The FHF just didn’t impress me, the harness always felt like it was slipping, and the chest pack always seemed to slip down and become a belly pack.
I really like my AGC, tons of storage, and it had a sleeve on top that would hold your phone and keep it easily accesible. I didn’t like having the lid fold back, and if I put my binos in just right they would squeak against the fabric on the inside. Mine was the older style that also had a buckle closure for the lid instead of the elastic cord and hook. I hated having a buckle.
I really like my marsupial, even though there’s stuff about the AGC I miss. There isn’t as much storage space, and the rangefinder pouch doesn’t hook to the pouch, so it ends up sliding around a bit. I also had my wife pull the elastic sleeve off my AGC and see it in the marsupial. I do like the fold forward lid, the magnet is relatively soft and quiet. But the other bad thing is the magnet messes with your compass if your using one. The harness is comfortable, and the exterior and interior fabric are both nice and quiet.
All in all, I’ll stick with the Marsupial. The fold forward lid is a big plus for me.