I would like to settle on a tool to create/maintain my custom eclipse distrib (starting with next 3.6). By studying previous questions main contenders seem:
I was in search for something like that myself (but more driven by the shared team approach), and I highly recommend the new Yoxos 5 Beta. It features synchronization of plugins and settings, while all your other suggestions only synchronize either plugins or settings, if I remember correctly.
In addition to your list, it might also be interesting to have your own mirrored update site, so its easier to control which version of which plugin can be installed at all (that also being more important in a corporate environment). See Eclipse help for details on how to create that mirrored site.