I currently own 4 vB's and 1 IPB licence. Hands down vB is better. I bought IPB to make styles to sell (I design skins) and it's much more difficult to modify IPB. Also, there are ten times more modifications on vB.
Vbulletin:- Easy to modify the templates and style
- More modifications
- Better support
- Less expensive
- Better portal
IPB:- Profiles more like Myspace
- More modular (everything is added like a building block)
- Better control panel
- Blog and gallery are made by IPB
Trust me, if you want ALOT of features and more for gamers go with vBulletin. I bought IPB before they raised their prices or I would have never gone with them. vB's portal (vBAdvanced) is so much better then the one made by bfarber for IPB. Buy vB and then make sure you thank me. LOL