JVM is slow as heck to start, but an awesome runtim. In an ideal world I'll never have to restart my application or my repl, but in the real world I do it all the time. It's much faster than node.js/V8 when executing heavy tasks.
One reason I might be interested in running clojurescript on node.js is because most web technologies nowadays are written for node.js/javascript first and ported as an afterthought. GraphQL servers on Clojure/Java, for example, are like 3rd class citizens compared to node.js. Google provides nice wrappers to their APIs as long as you're not using clojure. I end up writing things in-house a lot more often than I would with node where I just npm install the package I want and I get something that is maintained by the official author.