Re: Switching to WordPress from Joomla, forum security issues?
Having run sites with WordPress, bbPress and Joomla, I have had less security issues with WordPress and never one with bbPress. bbPress is certainly less used, so it’s less of a target (like Apple for viruses, for example.) WordPress security releases seem to be fixed fairly quickly. There was an update this week to 2.8.6 for example, to fix some security issues.
I’ve done 3 sites with Joomla and about 40 sites with WordPress, and 3 bbPress forums. I would never recommend Joomla to anyone either.
Drupal had too steep a learning curve for me, and with 2.9 WordPress is adding custom post types, which was a strong point for Drupal in the past.
I would use WordPress. But before you install bbPress, define what you want in your forum installation, and post that here. Integration is not a strong point with bbPress and WordPress right now. If you desire integrated logins between WordPress and bbPress, you might want to consider a WordPress forum plugin instead of bbPress.