htm is looking to act as a convenient alternative to jsx to fit the workflow of folks in react/preact land. lit-html is more of a whole new thing that is technically similar, but not coming from the same place in terms of developer experience.
One other difference in practical terms
htm:
As of 2.0.0, htm is stable, well-tested and ready for production use.
lit-html:
lit-html is currently in development. It's on the fast track to a 1.0 release, so we encourage you to use it and give us your feedback, but there are things that haven't been finalized yet and you can expect some changes.
From what I'd gather:
htm is looking to act as a convenient alternative to jsx to fit the workflow of folks in react/preact land. lit-html is more of a whole new thing that is technically similar, but not coming from the same place in terms of developer experience.
One other difference in practical terms
htm:
lit-html:
lit-htmlhas an RC release and is expecting a 1.0 release in January.Another potential perk of lit-html is it's backed by a team of developers at Google and is well tested by being used in Polymer/LitElement.