JRuby is still going to be slower than clojure, due to the semantics of ruby. All function calls are resolved at runtime, while clojure resolves as many as possible at compile time.

Foo::Bar.method() vs (foo.bar/method)

The ruby version does three loads from the heap, at runtime, while clojure does zero.

invokedynamic in JDK 7 will help narrow the gap, but the fact remains that Clojure was designed with more performance in mind than ruby.