In my understanding currently:
- the stock server (Weston) doesn't know when a user moves/resizes a window until the client tells it, so there must be a round trip before any action happen: far from ideal in a WAN.
- Wayland has very limited server rendering, so to be able to have XRender-way to display text, you'd have to change it significantly, until then Wayland will use much more bandwith to display text than X (if the toolkit use the XRender extension of course).