I’ve tried packs from both Zpacks (Arc Blast) and HMG (Porter, Southwest) among others.
I normally go out for 5-9 day trips in the Sierra and food weight is the main factor in the initial days. I base my comments below on that specific use case. YMMV.
Zpacks packs seem to be best suited for carrying under 25 lbs total – the pack also doesn’t hold a bear canister (BV500) well. Over 25 lbs in it was torture. The DCF material on the Arc Blast seemed fragile – I wouldn’t be comfortable taking it off trail where it might contact rock. Many of my trips are off trail and involve some amount of scrambling.
HMG lacks (lacked?) any load lifters making adjustment and fit pretty awful. I had the 4400 so it held the bear canister well. But beyond 25 lbs I found it quite painful though not as bad as the Zpacks Arc Blast.
I settled on Seekoutside packs as my go to packs for my typical multi-day trips: adjustable, pretty ruggged, and well made.
I did try both the ULA Catalyst and the Circuit. Both excellent packs – very well made, good material, adjustable and carry well. The Catalyst is what I would get for myself given my need to carry a full sized bear canister. I found the Circuit to be an excellent pack except for the fact that with a bear canister in it, it’s a very tight fit. Both the ULA packs fit and carry like a dream with up to 35 lbs total weight.