I cannot speak to the larger packs, but I really like my SG Avail. I am a bigger guy and this pack is more comfortable then the Kifaru I was previously using. If you have really broad shoulders SG might be worth further investigation.
It's hard to beat a well made 20ga or 28ga O/U or SxS. I always think of quail and dove hunting as a time to let the "pretty" guns shine as there is less chance of beating them up on these hunts, at least in Texas. Most of my hunting group employs break guns but there is always someone with an...