Of two choices, light weight, I'd say Seekins. Quality is going to be similar. I'm a little biased obviously since we have our own sources for our builds, however, we are dealers for Seekins and Wilson and have always enjoyed working with Glen and his team. Aside from that, you'll get a gun that shoots very well either direction you go.
If we were to build one we'd offer the 20" with a double fluted barrel to help save some on the weight. It's roughly the same weight as a 20" carbon fiber barrel; the biggest difference in felt weight will be in the stock and handguard you choose.
Have fun shooting regardless. The ARC is a joy.