These two quilt designs share a number of important features, while also appealing to each their unique user group.
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:
20°F and 15°F options available
Draft collar at the top opening
More size options
Easier vented foot section
More fabric choices
What is unique to the SULO:
40°F option available
Longer closed foot section
Less beginner suited