I've seen some major display errors on VB. Nonetheless, though, it might just be due to lack of updates. However, besides that stuff, I cannot really make a strong opinion on VB. Anyway, my affection for XenForo is mostly driven by the fact I have the most experience with it. In other words, it's what I'm used to.
Oh, by the way, regarding the third one, IPB, I have nearly zero experience with it so I cannot comment, but based on what others have said it seems to be a solid product competing with XenForo and VB on an equal playing field.
Personally, I prefer XenForo and the main reason for that are the prices. IPB can cost over $350 if you want several different modules added to the main IPB software. For some reason, they also require you to buy the Forum module seperately even though anyone that uses IPB use it as a forum. Plus I feel like XenForo feels a lot quickly and less bulky compared to IPB.
The price on Xenforo is fair, even with the updates. I mean, the updates aren't always 40 USD, they go down for repeating customers, and the price for an entire extra forum goes down also, from 140 USD to only 110.
VB is the worst option these days as VB 4 and 5 were total busts. The hardcore VB fans hate it. The modders and addon devs have pretty much left the building too. Their customer support is also really bad. I was a ten year customer and couldn't get good service even if I paid for it. Was happy to sell my licenses.
I don't let my clients use VB since they're on the decline and it's just a hassle dealing with it now.
I've used Xenforo. It's fast, lots of addons available with new devs coming in, and the customer service is really good - that's a huge plus.
I can't speak for IPB as I haven't used it yet.
I will backtrack on my original statement a bit. Note, the quoting function on VB isn't as good as XenForo's and that's reason enough to not want VB. However, though, there might be some mod that fixes it.