Just a suggestion, if you'd like a full dedicated XBMC, then I'd go with Raspbmc. But if you'd like to use the Raspi other than XBMC, then installing it on a debian or other distro would be best.
For a "minimalist" choice, I think XFCE is the way to go. It really comes down on personal preference. You gotta try them all before you make a decision.