GASP. I'll have an Insider Extra for Monday ;)

Because XCM is for the more hard core De´Vo worshiping kids whereas cardistry is more laid back and well.... Cool.
In all seriousness XCM is more complicated and is more about control and pushing the limits mostly by Perching(balancing packets on outjogged cards). It´s more complicated and utilizes a more disciplined act.
Cardistry on the other hand is more of a performance art which aims to be more fluent and beautiful for the eye. You can look at it as a Gambling techniques(which need a great amount of skill and coordination) and well executed close-up magic(which is magical fluent and does not put emphasis on whats going on with your skill set).

M.