The equivalent of i3 on Wayland is Sway; it’s even compatible with i3 config files, it’s a true successor. Hyprland is popular because of the eye candy and its rapid adoption of features which patch over some of the gaps in Wayland functionality. However I think those advantages have become fewer and farther, I personally use sway and if I wanted the visuals I’d use the swayfx fork

Mostly, yes, X vs Wayland. Hyprland also has a lot more eye candy in the way of window animations for snapping, dragging, etc. I find the Hyprland config file simpler too, but that’s just me.