From my point of view, Unpoly is just more "full stack" than the others. You have the functionality of several of the others in one single package, plus awesome

From my point of view, Unpoly is just more "full stack" than the others. You have the functionality of several of the others in one single package, plus awesome things such as automatic loading indicator (turbolinks style), very good error handling, modals, layers, popups, sidebars, slow network detection, caching, eventbus, server provided instructions via custom http headers, polling, keeping elements across page transitions, compilers (kind of "stimulus" for creating custom behavior based on html attributes), etc. And all of it in an awesome and very clear API: It's all custom and data attributes on standard elements. HTMX, in my opinion, has a smaller scope. Of course you can do everything, but you'll have to do more yourself. Alpine seems to be even more low level, kind of a lightweight Vue. I don't like it, it really turns me off adding code in html attributes.