I can't make an informed comparison[1], but check out http://ideolalia.com/performance-in-clojure-and-factor - the author uses penumbra (clojure's gl wrappers) to offload the vectorised computation to the GPU.

That plus clojures inherent concurrency support seems like a pretty awesome mix to me.

[1] I've used lots of python and some clojure but never done heavy numeric computation in either