- Appearance: XenForo is slicker. VBulletin's look is quickly becoming outdated. I would never use VB's default theme. XF's default theme, on the other hand, is quite appealing.
- Customization: I was able to customize XF easily. The customization interface is better organized than VB's.
- Intuitivity: Not an actual word, but XF takes the cake here too. If you've never seen VB's backend, you're in for a nasty surprise.
- About the CMS: Yes, VBSuite offers a CMS solution. No, it doesn't work well. At all. It took VBulletin over a year to implement comment linking (ie, same comments on CMS and forums when a thread is promoted). When it was eventually implemented (4.1.11), it desperately needed a patch (4.1.12). I've yet to experiment with XenPortal, but it looks great.
- Server load: Untested for now. We shall find out when I switch my largest forum (VPS at 60% load, 2.5GB RAM).
- Addons/mods: VBulletin takes this one. Keep in mind, XF is very young. VB is a mature product that developers have been working with for years. I LOVE how XF allows developers to sell addons/mods through this site, such a great decision on Kier's part. With time, I believe XF's developer base will be second to none. This move centralizes most mods, which is great for developers and users alike.
Those are my thoughts. I'll add to this as I keep experimenting with XF. Can't guarantee XF will always come on top as I try my best to remain impartial.