First, let me say i have never had the privilege to code a vbulletin. I do maintain a couple of Phpp forums, though. The problem with phpbb is that when a new version comes out, which seems to be once a month, you have to reinstall the changed files. If this includes files you modified, then you have to make sure not to break the modification. It's not necessary to upgrade, but, if you do... it's a pain in the "hello!." In addition, there isn't as much support for phpbb, so if you encounter a problem you have to rely on the phpbb forum, which is, in my opinion, COMPLETE CHAOS! There are a lot of interesting styles for the phpbb and they are easy to customize. Considering it's free, and that i've never used VB, i would suggest phpbb for its easy to understand structure.