The dies and mats for the Baby will work in the GO. The dies and mats for the GO will work in the Baby only if they are no more than 6 inches wide. If you are considering getting one, I would get the GO. I have it and the Sizzix Big Shot Pro. I use the BSP more because I can use most of the Studio dies in it and it is easier to use the hand crank. This web page will tell you the specifics of the Accuquilt cutters (the size of the dies they will use, etc.).
http://www.accuquilt.com/fabric-cutter-comparison