I will go with xenForo I used both, but xenForo is really a much faster forum software. Also, if I were to compare xF and vB's responsive design, xF is so much ahead of vB5 in terms of speed. Just my 2 cents.
I can't speak about Vbulletin. I've never personally use them before but they are often complained about online so I'd likely never buy from them. I have a current XF licence and a recently expired ipb licence. Xenforo is a great software and is certainly a speedy one that is attractive. However compared to its competitors, the software is a bit basic. If you need solely a forum software, then XF is a great choice. Personally my site utilizes a chatroom and I love the fact that IPboard has a chatroom add-on that they host and maintain(alleviates me from having to worry about it) and it integrates perfectly with the site as well as it has other add-ons that integrate perfectly. IPboard isn't as Flashy by default like XF but it is way more powerful software in my opinion. 3rd party development for Styles and Add-ons with XF is decent but I will say that for the simplest of things, I've notice developers like to charge high prices. And a lot of the xenforo styles are incredibly tacky in my opinion and people want 20-40 dollars for them. I prefer Ipboard's 3rd party developers for styles and add-on because prices are fair and the products are supported well. I'd recommend XF only if you want basic forum and Ipboard if you want more control/power.
