Plug either adapter in and upon establishing a connection, Wifi turns off (if it was on) and the wired interface becomes the default interface and default route. Remove the adapter and everything reverts to the way it was.
Most apps I tried with the wired connection worked fine, but some did not - most notably Fing Network Tools. I was really hoping that Fing Network Tools would work better than it does with the wired connection. I've already made suggestions to the Fing developers to better accommodate wired connections.
For $17 you can turn your Moto X into a basic network troubleshooting tool for wired connections using LanDroid.