I received an EB First Ascent sweater last month as a business gift. I've owned a Marmot Zuess for 2 years and have taken it on 2 long backpacking trips. At first I didn't even consider comparing the 2 because I didn't consider EB as a serious player. My son-in-law told me that the First Ascent line is serious stuff, so I started seriously comparing.
I'm impressed. This is a great down sweater with an excellent warmth to weight ration. As others have noted, it's very difficult to accurately compare warmth, but subjectively, this is just as good as the Zuess and weighs 1 oz less. I like the DWR finish on the EB. The best feature is the fleece lined pockets; such a nice treat compared to slippery nylon when your hands are cold.
I'm still not sure which sweater I'm going to take on my next backpacking trip. It's nice to have a choice!