This is a good conversation, it might help some one decide.
LOL! I only use the back pack when doing a day long trek and pack my lunch, water, and any extra clothing/jacket I may need. Typically I only use the chest pack.
I tried the slings. They got in the way more than anything and deep wading sucked since they would get water logged
I felt limited with having to move it around all the time. The Chest pack was always in front and worked great as an arm rest when tying stuff up.
Actually the High Country can be worn as a sling too for those interested. It comes with two different sized neck/shoulder straps. I only wore it as a chest pack.