It's an interesting choice because each has it's PROs and CONs.
- uncompressed the Klymit is bigger
- compressed about equal volume
- Klymit is a blanket with snaps, foot box, and hand boxes.
- STS is a sleeping bag liner with a 1/3rd zip and a shock corded hood
- STS is mummy style with a little stretch
- Klymit weighs 1.5lbs and the STS weighs half
Getting in/out of a sleeping bag or a liner, in a hammock, is a serious challenge to be offset with the blanket falling to the wet or dirty ground.
In a tarp+bugnet sock the Klymit adds distance between you and the bugs but it's easy to be exposed. Where the STS can be chemically treated to ward off bugs and will stay put.