Even the support team at vB5 says vB5 is better as a packaged platform. So if someone wanted to start a forum, vB5 may offer more than what XenForo offers as a standalone product.
Then there's the support issues, like this customer who paid for vBulletin's cloud services so it was all fully managed & supported by vBulletin:
https://www.youtube.com/watch?v=zMnavb--lM4
Listen to his story. He was ignored. XF's Developers swooped in to help him migrate over to XF.
My opinion of vB5, it's a bloated platform. It's like buying a brand name PC: HP, Lenovo, Dell, etc.
Where it comes with all the extra software that makes it feel heavy.
I prefer the customizability, like PC enthusiast who custom build their PCs. Sure it cost more in the long run, but it performs much better when it's exactly tailored to you, and not just the general public.
I've switched to XF myself.
You should see this too:
https://www.theadminzone.com/threads.../#post-1158138