7.04 is still supported. Non-LTS releases have 18 months of support.

6.06 receives security updates only so the software selection is by now badly outdated. That's not to say that you can't find software for 6.06, but security support is not the same thing as running an up-to-date distro. There have not really been a lot of years of development on 6.06. There has been a lot of time to find bugs, but most of the bugs were not fixed, because development takes place on the new releases.

If it were me, I'd run 7.10 if I were going to run Ubuntu. Or else wait a few weeks and install 8.04 for a LTS release.

Vector indeed has great package selection. I don't see any choice over vector here.
I agree Debian and others provide too many package choices. But some times a person needs some software that just works.
For example, Few people installs OpenOffice, KOffice together for office work. Similarly, a regular guy doesn't need more than mplayer and VLC (for video), Amarok (for audio) as multimedia application.

Choice is very good. But When I am concerned about a fast distro for an old machine, I see Vector is the fastest here (never tried Xubuntu among the listed distros). With all popular packages available in the distribution repository, I don't think you should look other than Vector.

My second vote will go to Ubuntu 6.06. But don't use Ubuntu 7.04+ series. They are fast becoming a bloated and heavy distro. Ubuntu soon will become XP of Linux world, if not Vista (Still want to try v8.04 though).


My suggestion: Vector Linux/Xubuntu 6.06