*looks at last post and sees that its not a month yet since the last post was posted XD* umm, I hope I am not reviving this thread or anything since its not been a month since the last post yet.
Anyway onto the topic at hand, I think VBulletin (if I just said VB, I would think of Visual Basic XD >_> ) is very good and one of the best forum software however it does cost too much imo (its what I voted, the cost option).
If you have the money, I would suggest getting VBulletin since it probably outdoes all the other forum software in terms of security (although I think SMF has/is catching up with it, not sure on that but I am not a fan of SMF software anyway)
However, if you know how to make your own forum and have enough programming knowledge, I would recommend for anyone to make their own just because then you get total control since its all your own work. Plus you don't have to pay to make your own unlike if you bought something like VBulletin or Invision Power Board
Umm, I suppose that's my take on this anyway.