@4ester said it well in the first post:
In fairness, most all of the pack brands have a target audience and tradeoffs.
If you want a pack to be rugged your choices narrow just as if you're looking for the lightest possible pack that can still pack out meat
on your hips. For me, the bag needs to have a load-shelf or meat hauling system other than just the pack. In general lighter the pack the more fragile the material, so you need to know that going in. I'll put more weight in my Elk gun with an FFP etc to ensure it is the very best it can be, but I am going to gain that weight back by making other "concessions" in my pack and gear.
For instance, I would say my Kifaru was robust and handled weight well, but a bit heavy at 7lbs, my Stone Glacier super light, but damn the hip system did not carry quarters very comfortable at all (on my hips, compared to Kifaru). My Kuiu, while obviously the least robust bags (because comparatively speaking, most of the weight is in the harness system), but about as light as my Stone Glacier, carried the weight with the big hip belts and CF frame far better, and saved me about 3lbs over my Kifaru, now that rifle feels lighter
.
If you're banging through the brush and dragging across the rocks and want the bag to look new for years, the Kuiu bags are not for you, heck even the SG maybe not. For someone like me who wants to cut ounces on the pack and pack in contents, but still carry out a lot of weight, the Kuiu harness and load-shelf (meat hauler) works well. If you're really rough on gear, you're not going to like ultra-light bags of any kind. That said, I am not real rough on my gear, and don't mind buying new stuff when I am, but we all must find our balance, my 21oz 50L ArcaZip from Zpack is crazy fragile and not suited to carrying meat out, so I chose only to go so light. Just trying to add that each signature pack in these brands will be liked better by the user if they account for the strengths and weaknesses.
Packs you listed that I've used in the same relative class - size and use
For Ultralight packs + *Game Hauling (Pack system in the 4lbs range)
Stone Glacier - Note they have some way heavier frame systems now since I had mine, but sure to carry better.
Kuiu - better hip system but lightly more fragile bag than SG I had.
For light + *Game Hauling (add a pound to the above)
XO (only tried a hunting buddies, but it is very nice)
For Robust bags + *Game hauling (add 2-3 pounds)
Kifaru - hauls game well
Hated the weight class - most things about the bag system
Eberlestock
* These bags all have load-shelves or ways to detach the bag from the harness and frame allowing the user to either hall out quarters between the back and frame or remove the bag entirely to haul meat.
