While I have not used either, I have read many times the mk 2 is superior in almost every way.
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=687&Camera=453&FLI=2&API=0&LensComp=242&Sample=0&CameraComp=453&Go.x=11&Go.y=10&FLIComp=0&APIComp=0
This is a fantastic tool. Check out the CA on the mk 1, and how much sharper the mk 2 is.