[cheat-master30]

vBulletin in my opinion is by far the best option for forums, but you can pretty much expect me to say that, this is vBulletin.org. Never the less, first off, there are I think three or four things vBulletin has which no other boards do as well:

1. A great template/style system
2. Easy adding of modifications as plugins/products
3. More indepth controls for users, forums, permissions, etc.
4. Support in any way, and other such stuff.

In terms of features, there is a lot less difference between vBulletin and Invision Power Board than there are between vBulletin and other forums, and while I'd say vBulletin offers more out of the box, I'd also say that both forget to offer features the other does and vice versa.

Don't even consider phpBB for a forum which keeps up for things like features, security, etc, it's still behind pretty much every other mainstream alternative in things like that.

All in all though, you compare them and choose, although there's only really vBulletin I'd truly recommend.

P.S. I'd also say vBulletin increases forum activity, with about a 1000% activity increase for my own forum, but then again, I did go from free hosted forum on Invisionfree to paid vBulletin forum on a proper domain. Still think vB helps activity in this regard though.