I dunno, I tried both on my server, and I thought Drupal was a little easier to use, and you can plug in almost any type of addon you may need. To me this makes it a better choice as you can start off small, and add as you need to.
However, if you want to test it for yourself... opensourcecms has live Demo's for you to check out, and you can look at a number of other choices too.... IMHO opensourcecms is the only way to check out this info ...
I tend to find drupal a lot easier and lightweight.
Joomla just delivers a lot of stuff that i never have the use for. Drupal on the other hand lets you download that extra stuff if you need via modules.
Community wise both have buzzing support groups, Joomla is shade better i guess.
As someone said try both. Set up a localhost and get your hands dirty. You will know which is best