User explained it in a thread here while back,Aromasin only controls from 60-80% of your estrogen,it doesnt "kill" it and it wont be a rebound after you quit taking it,it slowy rises or stablizes but Arimidex kills off estrogen totally,IMO aromasin is easier to manage your levels while on cycle better than the other 2 within certain limits,if you are bad to get really hard gyno the other 2 may be a better option,all people are different though,
Plus,i know it may sound strange,but Aromasin has some of a libido kicker to me,not a whole lot,but it does seem to help me in that contrast