These two quilt designs share a number of important features, while also appealing to each their unique user group.
Common features:
ETC, differential cut, mummy style permanently closed foot, advanced baffle design, properly filled down chambers, real life size measurements.
What you get with the Arc UL that is NOT present with the SULO:
Beginner friendly
20°F and 15°F options available
Draft collar at the top opening
More size options
Roomier fit
Easier vented foot section
More fabric choices
What is unique to the SULO:
40°F option available
Lower weight
Lower price
Snugger fit
Longer closed foot section
Less beginner suited