More than 5 years later my opinion hasn't really changed all that much.
If a migration happens, i would still vastly prefer a proper forumsoftware. I still like Xenforo, at least the one i am very active in. But i also see that Xenforo development has somewhat stalled. But in that regard it isn't much different that SMF

My favorite aspect of XenForo is it's seamless scaling from portrait-mode smartphone screens to wide PC screens, and no reliance on a *completely* different mobile view.
My main gripe with SMF is the image upload and the quoting system.
Just pasting images from your clipboard to the forum is such an easy way of handling images.
The KiCAD Forum is one example of a Discourse forum that i know. And it's usability is atrocious. Just alone that it doesn't properly paginate and has an "endless" scrolling overview is crap.
EDIT: And if a micration to Discord, of all places, would happen, very likely me and a lot of other people will be out. Discord is a blight on the internet. It has killed so many open forums and essentially removed them, and all their accumulated information, from the internet. Discord is a closed system that you can only access with their client, and only after you have registered and are invited to the actual community. It's essentially a chat service on steroids.