Games usually don’t go through the traditional compositor cycle of Wayland anymore so there shouldn’t be a difference.
For non-gaming usage Wayland should actually be better for battery life as the protocol is less chatty. Though of course it depends on which implementation you use.
“Though of course it depends on which implementation you use”.
Also, wayland is huge in the embedded sector, e.g. many car display uses it, specifically because they cheap out on hardware, but wayland still runs just fine, unlike X.
