I've always been an SMF guy, could never afford a vB license back in the day when that was the go-to option. But over the lockdown I had a good bit of cash lying around and really wanted to splash out on a nice piece of software, so I went with Xen knowing a lot of the vB folk are responsible for it.
I've been delighted with it so far! I was pretty easily able to transfer all my features and stuff to Xen. I didn't have as much trouble getting used to the Template system than I thought I would, since with SMF I'd just open the source files in an editor and upload them with FTP instead.
My only problem so far is I'm struggling to understand Xen's addon system. SMF used what I assume is an older version of PHP that is way easier to understand, and you can kind of just drop SQL queries wherever you want. Xen isn't so simple, but I've also only had it for maybe 2 months, so hopefully it's simply a matter of time before I get a grasp on that area.