There is often a debate on which aromatase inhibitor is more effective or safer to use... The biggest debate is that of aromasin vs. arimidex... Some few little difference while others understand the gap is significant... What I can say with a million percent certainty is this... Aromasin is a suicide inhibitor where as arimidex is not... What does that mean? It means that while aromasin kills estrogen, arimidex merely suppresses... for some, all they need is suppression and control however, for many, that simply is not enough and the gyno prone users find that arimidex use can still lead to the development of gynecomastia, which we all know is something NONE OF US WANT... does that mean arimidex is not effective? NO, it certainly does not but it does mean that it is not as strong as aromasin in blocking out estrogen... some feel that aromasin can crush estrogen, and theoretically, if misused, it could but anything that is misused can lead to problematic occurrence... Simply put, if you are gyno prone, why would you even risk it? In fact, even if you are not, why would you still leave the door open for any type of side effect, especially one that can cause the internal, external and mind throttling effect something like gynecomastia can lead to? For me, it is a no brainer to use some sort of protectant anytime AAS is in play... Even if there is a small to none chance of estrogen conversion, one should be on hand and the rebound effect should always be something you are aware of... The choice is yours on what to use but for me, i stick with aromasin as it is tried and true for my needs...