Originally Posted by Muxster

To address the main question, what is the difference between the "X" and "CX", you can look at the parts list on the John Deere website. As far as the 300 series, they all use the same "mast". The part numbers are the same. The 300 and 300X use the same "boom" and the 300CX has its own boom. The bucket cylinder and boom cylinder are different for each model. The difference in cylinders between the 300 and 300X are bore diameter (X is bigger and the stroke is the same). The difference between the 300X and 300CX cylinders is the stroke which is different on the X (the CX has another knuckle between the boom and bucket).
I'm guessing the 200 series is the same.
In theory they are interchangeable since they all have the same mast. The difference is the bigger cylinders would require more pump flow to have the same travel speed. The larger cylinder bore can deliver more force (hence the bigger capacity spec).