its simply more practice problems. how comparative it is the actual dat I'm not sure.
some say its great and just like the DAT. others say CDM is better.
from the tests I've done I think both are similar to each other. I give CDM the edge merely on the fact that it is computer based and will get me used to work on a computer.
Its is an extra 50 bucks. Unless money is super tight for you. But to me $50 is nothing. I can easily waste 50 dollars on something totally useless. If extra 440 problems raises my math score by just 1 point then it is worth it to me.