Wow... It’s been almost 16 years since I last touched vBulletin. Looking at it now, so much has changed. I feel like it wouldn't be fair to just compare them in terms of pros and cons; every forum script has its own ups and downs. Besides, vBulletin hasn't just been sitting still all these years; they’ve definitely evolved in their own way.
But to be honest, XenForo just feels 'right' to me—both structurally and in terms of daily use. The best forum is the one that doesn't restrict us and lets us customize every bit of it effortlessly. Technical support is another big one. You need to know someone’s got your back. As a site owner, you have to be ready for anything; so, quick security patches, fixing bugs, and a platform that’s always open to improvement are the deal-breakers for me.
Having started with vBulletin and eventually moving to XenForo, my main reason for choosing XF is the team. Knowing that the core crew from the pre-acquisition vBulletin days is here makes all the difference. I trust them. They really know their craft.
Also, a quick tip: you really need to use a forum script for at least 6 months before you can truly judge it. You just can't make a solid decision based on a first look.
Side note: It’s been a long time since I logged in, and I just noticed I have three old 'vBulletin 3' licenses sitting in my Member Area. Funnily enough, the renewal price is exactly the same as buying a new one. I guess if you step away for 16 years, you just have to start from scratch!