The "RC1" you saw stands for "release candidate 1." It is probably the Xfce edition. AFAIK the KDE and Flux versions are not released yet. Well, KDE might be, I do not know, I stay well clear of KDE. There is also an "unofficial" debian version which they are calling GLACIX. I guess that is the only debian version? It gets complicated. Which one should YOU use? Lol, while I am at it let me tell you which car you should drive!
I use the Xfce RC1 edition and I can assure you it is fine for use. In fact, I would call it the most perfect Linux distro I have ever saw! Before that I used the Gnome version for a few weeks. I installed and ran Xfce on top of Gnome and it worked but I had a few problems. I am sure if I had just run Gnome it would have been good. Take your pick.