Personally, I don't find the Stone Glacier packs comfortable, but I don't like fits-all frames. The SG packs feel like a stiff "trapper nelson"or "Alice" frame to my back. MR packs are "ok", but again, have gone to a fits all frame system. I definitely like MR over the SG packs. Of those you mention, I'd go Kifaru, hand's down. I far and away prefer the ability to fine-tune stays to get the fit I want.
However, I'd go with a Seek Outside pack over any of them. I dislike a few of the changes they've made, but they're damn comfortable and well thought out, as well as being light.
