Aromaxyl is a type 1 suicidal aromatase inhibitor. It kills estrogen or a good percentage of it. Aromaxyl also boosts natural test levels by a significant amount and can be used with nolva. Arimidex and letro can both significantly reduce the effects of nolva. It has no adverse effects on lipids either.

Arimidex is a type 2 aromatase inhibitor and works slightly differently by suppressing the conversion to estrogen in the first place rather than killing it once it's been converted which leads to the possibility of rebound gyno symptoms. It's also not as effective at dealing with excess estrogen.

I suppose it really depends on how much estrogen you are producing and how much of it you want to get rid of as to which AI you prefer. I prefer aromasin because I think its better all round. I definitely don't think its a worse choice.