I converted over from vB4 to XenForo a few years ago. We had used vB3 for quite a while before that, so I've got some experience.
In my personal opinion, there are dozens of reasons to switch to XenForo from VB4 or VB3.
Better Administration
- The control panel in vBulletin is a nightmare, I always felt like I was digging through settings on a linux PC from the 90s. XenForo's control panel makes sense, it's crazy simple, and works great.
- vBullettin's template modification system is a pain in the neck to work. Making changes on our vB3 forum always took days to get right. XenForo does the same in minutes.
- Getting around the vBulletin system to moderate users, posts, etc is like trying to fix your car on the side of the road during a rain storm.. The inline moderation of threads, users, and posts in XenForo is genius and always works flawlessly.
I'm constantly surprised by the no-nonsense layout in XenForo. Not just for me, but for the users as well. People know where to find things. You can't really put a price on that.
Efficient Code Written for Modern Web Standards
- From what I can tell, up to VB4 (and maybe VB5), the same code base was used since VB1. They never took the time to rewrite the software from scratch for modern standards and it shows. It's the same issue as Windows. Decorate it all you want, people can tell your core system was built in the 90s.
- The modern coding used in XenForo allows it to take advantage of new technologies in a practical way. Our forum saw an increase in users sticking around longer as well as increased traffic from SEO. We saw faster load times and the horrible feature creep vBulletin software seems to be smothered in is nowhere to be found.
- Honestly, the biggest advantage here is it keeps your forum relevant. Users want to know that you're keeping up with web standards for the sake of security and usability.
With better administration and better code, you spend less time banging your head on the screen trying to get forum software to do what you want and more time actually engaging your community. Which is what you should be doing most of the time, anyway. These behind the scenes changes aren't going to bring night and day difference right away, but they pay off within a few weeks.
Less Frustrated Users
As for the users, I've found we get way less e-mails wondering how to get X done on the forum. The XenForo layout of things just makes sense. You wouldn't know it, but tons of people get frustrated with websites over hundreds of things like the navigation, page load times, and arrangement of features. They don't send you an e-mail, instead they just leave to somewhere that meets their needs. In this respect. XenForo gets it right. User's don't leave frustrated because the software is GETTING IN THEIR WAY. The stick around because everything does what it claims to. From my experience, vBulletin fails horribly in this regard.
*steps off soap box*