I like vbulletin its a staple in forum communities, don’t see any reason to change it, but you could certainly customize/mod it some more.
And I think you should allow avatars though.
And like Unity I also think you should add board view avatars showing for thread post and last post users… Forum Display Enhancements - User Avatars In Thread Listing - vBulletin.org Forum
Is plenty of addons for vbulletin that will bring it upto having some of the built in features that Xenforo has… its best feature being the alerts/notification system using ajax… its by far the best feature of Xenforo and puts it ahead of the some of Western forum competition for that alone.
Anyway Unity have gone back to Xenforo, but with intentions of shoving that modern junk Lithium at us again. So maybe I might still be coming back here again… thinking of switching to Unreal next month but not sure.