haha... CrM = Monohydrate
I love reading studies, I love arguing, and I love learning and if that means being corrected, then so be it... but from the studies I've read (countless), I can say that Monohydrate is the most tried and true version of creatine you can find.
Why do new forms of creatine come out? - I guess I can't answer that question without a dollar sign popping into my head. As far as CEE and Kre go, I'd rather not take creatine, than submit myself to one of them (perhaps that's being ignorant..which I wouldn't put past myself)
This is straight from LN on the effets of CEE
CEE is claimed to provide several advantages over CM because of increased solubility and stability. In practice, the addition of the ethyl group to creatine actually reduces acid stability and accelerates its breakdown to creatinine. This substantially reduces creatine availability in its esterified form and as a consequence creatines such as San CM2 and CE2 are inferior to CM as a source of free creatine.
Here is a review on the studies of Kre
In contrast to the claims of All American Pharmaceutical and Natural Foods Corp., the rate of creatinine formation from CM was found to be less than 1% of the initial dose, demonstrating that CM is extremely stable under acidic conditions that replicate those of the stomach. This study also showed that KA supplementation actually resulted in 35% greater conversion of creatine to creatinine than CM. In conclusion the conversion of creatine to creatinine is not a limitation in the delivery of creatine from CM and KA is less stable than CM in the acid conditions of the stomach.
Both of these studies were done by Tallon and if you want the full study just let me know.