My only advice is to get a pack from one of the several quality makers, that allows you to bend the stays for a custom fit to your back contour.
I own a kifaru with the aluminum stays. TO my knowledge, it is the only one of the major hunting pack makers that offers that option. Not saying a stock composite Kifaru, an EXO, a SO reveolution, SG X curve, etc..... wouldn't be exactly right for you. I'm just saying that 6 ounces to a pound and a half of pack weight means absolutely nothing but to satisfy the bean between your ears. It is much more important to have the PERFECT fit verus brag about how light your pack is when we are talking a pound or two. And, the only time you will notice that extra weight is when you pick it up to shoulder it. It won't be felt on your back. I promise.
Buy what suits you but know this. If everytie you stop you find yourself wanting to get out of the pack harness, you got an improper fit. The only time I take mine off is if I need something out of it, need to let my back dry or, plan to set for a long while. It is that comfortable. If you can't say that about the pack you choose, you need to find one that allows you fine tun until you do. Buy once right and be happy you did is my only advice. God Bless