[danh]

Firstly, Hiccup is Clojure (so basically server only). Cloact is ClojureScript, that compiles to javascript (so browser, node.js, etc).

Secondly, Hiccup produces strings. Cloact typically creates DOM elements, through React, that change every time a component rendered. But it can also produce an HTML string using the same data, to pre-render a page on the server using node.js.