vBulletin is ok if you can figure it out, but IPB is significantly easier to use and cheaper, and is also a much better (and less buggy) piece of software imo. That and you don't get screwed by license changes when you want to upgrade.
@OP: IPB3 was a complete rewrite; it literally shares no code with IPB2. The differences aren't too big from the user's perspective, but for admins, webmasters, etc., it's a huge difference.