Do you have the daypack lid for the MR, with the tuck away shoulder straps? Because the standard lid weighs in around 8-9 oz., not 14.
I would stick with the Metcalf. When you have it loaded up for a big hunt and then if you knock something down, you will be in good shape to pack it out. A 3, 5 or 6 pound pack doesn't mean much when you are lugging 80+ pounds out of the woods. Comfort and durability are king.....it is a slippery slope, and if you want to go all in on the lightweight thing, EVERYTHING has to be scrutinized. It gets silly and expensive quickly.