There have been a couple of very thorough posts on the subject recently that you might want to check out:
My personal recommendation would be to try out Julia v0.6, since it already has many of the best features that have come in since v0.4 (like fast anonymous functions, dot-call syntax, etc.). Also note that there is no v0.7 release yet, just a master branch that will eventually become v0.7 when it’s sufficiently stable.