X is inherently less secure due to the fact alone that, given enough time, new vulnerabilities will come out that will not be patched because X11 is EOL. Yes it has a different security model, but that security model is not very well implemented because X has an enormous code base that, at the end of the day is still not bug free (nothing is). There is a lot of legacy code contained in X that legitimately does not even have a function because there is nothing around today to use it.

Larger codebase = more moving parts = more code to exploit. That's the benefit to wayland aside from active support by the X/Wayland devs.