Looked at from a different perspective...
Embedded Linux is the one that works behind the scenes. It's the operating system in your router, your TV set top box, (e.g. Tivo) your digital camera, your Blue Ray player, your scanning radio, your car management systems, etc. Each version is tailored to perform the functions which the device requires and is therefore small and lean.
The other one's used on servers and desktops and is infinately configurable.