I don't know much about Wayland, but I know Mir is trying to be very efficient performance and battery life-wise even for smartphones, since it will be based on OpenGL ES 2.0. Can Wayland do the same?
> Other parts of the infrastructure used by Mir originate from Android. These parts include Android’s input stack[11] and Google’s Protocol Buffers.[12] An implementation detail in memory management shared with Android is the use of server-allocated buffers which Canonical employee Christopher Halse Rogers claims to be a requirement for "the ARM world and Android graphics stack"
I think Canonical wanted to be able to easily port Ubuntu to Android devices in the future. Will that be possible with Wayland, too? I think that's a pretty important aspect, because Android is the new "Windows", and there will be a ton of Android devices in the future, and just like Linux adapted to working on Windows machines, they will need to adapt to work on Android devices very well, too.
See:
* http://mer-project.blogspot.com/2013/04/wayland-utilizing-an...
* http://mer-project.blogspot.com/2013/05/wayland-utilizing-an...
Canonical started using libhybris without even crediting the author first.