Creatin Ethyl Ester, to my knowledge, is supposed to be a delivery mechanism, and it (the ester) is removed from the creatine in the liver purportely without hepatic toxicity. It is supposed to allow for better/faster delivery of creatine to the mucles, but this may not be the BEST delivery system available. Recently I was reading about something called a carbono-ester which is supposed to be a better delivery system with a lower potential stress on the liver. Monohydrate lacks this delivery system, and therefore is less likely to be absorbed–or absorbed to the same extent as CEE.
