At the time you last used vBulletin, two of the main developers were Kier Darby and Mike Sullivan who left vBulletin a few years after that and founded and started developing XenForo
A lot of people have moved from vBulletin to XenForo but of course there are still a lot of vBulletin users out there.
We generally recommend that people give our demo a try which is here:
Admin Demo. And of course try out some other software for comparison and base your decision on that.
As for WordPress, a lot of people use XenForo in conjunction with WordPress but there are also people who have replaced WordPress with various add-ons for example to add a portal (like a front page / news page) and article systems. These are third party add-ons but there are some high quality and well maintained ones.
Let us know if you have any further questions.