I’ve had a few, all have their good and bad qualities.
S4 lockdown: quiet, keeps binos out of the rain but the straps suck, they don’t stay tight.
AGC cub max: lots of pockets, locking straps so it stays where you want it. On the downside I’m not wild about the flap opening from the front, makes getting binos in and out sort of tedious. Also, material is rather noisy.
Rick young harness: this one gets the most use from me now. Weighs next to nothing, very configurable and about as bulky as a shoelace. Only downsides for me are that it’s hard to adjust unless I take it off first, and it’s just a strap so I have to be creative to cover my binoculars in the rain.
I’ve really been trying to cut down on carding unnecessary crap around while hunting, I run hot and my back gets sore easily when wearing a pack. Generally now I wear a vest with a few essentials and my binoculars. I’m one of those guys who can find a reason to fill every pocket I have with stuff I don’t need. The rock young harness is great for this. I really like the agc pack but it’ll probably see more future use where I bring my higher powered binos (glassing on the east side etc).