Just to further complicate the issue, I would recommend that you consider the Marmot Helium. This is a 20° bag in the same weight range (mine weighs 28.5 oz) as the two you listed and can usually be obtained at a lower cost. I have one of the older Helium bags with the half zipper. The newer Helium has a full length zipper; a feature that I wish I had on mine. Overall, it is an excellent bag and can be had in the "extra" length. I also have a WM Summerlite and it is somewhat less roomy in the shoulder area for me than is the Helium. I generally use the Summerlite unless I anticipate temperatures below about 30° for more than a night or two.