Drupal Forum or vBulletin or PHPBB

I have installed Drupal 5 and will be usinig it for portal that will aggregate content and also a user forum. I have experience with vBulletin and PHPBB, and I think that vBulletin is very good.

Can anyone take a minute to compare the Drupal forum with other pure forum applications.

One option would be to use Drupal for all of the context and vBulletin for the forum.

Thanks for the advice.
FB