the main one is that ymod is based on an old oscam, and the version is not current, while the D0scam is updated to the latest svn.
other difference is the shape, ymod uses oscam.keys that has its own particular shape.
D0scam uses a normal SoftCam.
other details you can read in the section on D0scam, where, along with the files, you can read and change the characteristics of each version.
Bye