I think the list of features says it all. They're not exactly comparable, are they? I don't think there's even anything preventing you from using both with e.g. React on the backend and Htmx on the frontend to load in the HTML that React generates.
Actually someone is already doing this. React components on the backend, rendered to static markup, sent over the wire to the frontend, which uses htmx. Someone tweeted about this recently.
