In the linux world, if you want the most recent software there is only an option: rolling release. That removes ubuntu from the list. I've found that keeping ubuntu reasonably up-to-date takes too much fiddling (adding PPAs) and removes a lot of stability.

Three of the most popular rolling release distros are: the debian-bleeding-based-bunch (never worked too well), arch, and sabayon. Sabayon beats arch in that the packages are signed (better security) and in that it can be installed much faster. I prefer equo to pacman, but that's personal preference.

The Sabayon community is great and the time it takes for them to fix the bugs I reported is incredibly short (!). impressive considering how small the dev circle is.

This is probably the best distro I've ever used. All my computers run this now.