Well, these are both Debian based distros. In fact, the only difference between Crunchbang and Debian is that Crunchbang comes with Openbox and a conky, instead of GNOME. Mint is so similar I can't even really tell the difference between them.
The whole damn Debian family is just 50 of the same distro with a different wallpaper and varying desktop environments.
If this is your first *nix experience I'd say go with Mint. Just as long as you don't even bother with Ubuntu.