I would go for XenForo. Did you know that, 2 of VB lead developer left and made Xenforo? Xenforo is the most hyped forum software out there right now. A lot of web dev have migrated their forum and used Xenforo, as of myself.
I was one a proud a vb user. But I migrated because of the following reason. Read below.
vBulletin Days and Nightmares
We have been running vBulletin for almost a 5 years and it served us well for much of that time.
In August 2010 we upgraded to vBulletin 4. That upgrade was, frankly, a nightmare.
I spent many, many hours trying to optimise the database, tracing slow queries and following bug reports. I also ended up installing Sphinx search, even though vBulletin seemed very slow at handling the results it got back from Sphinx. At first there were many complaints, some about things which we could fix, and others about things which eventually people just got used to.