It starts quickly because everything is lazy loaded, if you open project it will start language server, start indexing etc, It's definitely not much faster than IntelliJ, but functionality is still behind.
It does depend a bit on the language server. There are a few language servers that are nicer than the equivalent IntelliJ plugins, though that is generally not even remotely the case for JVM languages that aren't Clojure. AFAICT, the state of the union for Java is that it's not habitable without an IDE, and the only habitable IDE is IntelliJ.