Assuming you are referring to the two new 21.5" iMacs, there are a couple additional advantages of the 6 core machine: double the video RAM for example. However, I also have a warning. The base model of each comes with rotational drive - the 6 core model does default to a Fusion drive but the SSD is very small. Whichever you select, I strongly recommend you upgrade to an SSD. I also recommend that you upgrade to 16GB RAM since the 21.5" aren't user upgradable. (I've not seen any tear downs of the new iMacs so I don't even know if the RAM is soldered to the logic board or not.)