I've done fine on both of them. I don't see any difference personally in the way I feel and both do the job of lowering my estrogen properly. Only difference for me of why I choose Adex now is the lower cost due to less frequent dosing needed. I need half an aromasin (12.5) ed to get my estro to the same level as half an Adex (.5) e3d. I end up spending way less money on Adex vs aromasin

Can the whole rebound factor of Adex be avoided by just switching to ARO at the end of the cycle?
My joints are much much happier with adex! My knees took a beating while on ARO

I feel far better on Adex, especially on the joints but the over riding factor has me falling back to aromasin every time purely for piece of mind due to no rebound.

Oh and pharma where possible ;)

I definitely prefer aromasin. It works much better for me. The only issue I've run into is that it dries out your joints so I use glucosamine chondroitin for joint relief

Aromatase Inhibitors come in 2 types. Type 1 and Type 2. First Type 1 AI's bind by a process called hydroxylation; this hydroxylation process produces an unbreakable covalent bond between the inhibitor and the enzyme protein. Now the enzyme is permanently blocked even after all of the inhibitor is removed and can only be resumed by new enzyme synthesis. Type 2 Inhibitors on the other hand function all the same in their ability to reduce the binding process of the enzyme and the receptor. Except once the drug is discontinued or the concentration of the drug is sparse enough it is possible for the enzyme to seperate itself from the Inhibitor and eventually will allow renewed competion between the Inhibitor and the Enzyme for the receptor site. Aromasin is a type 1 AI and once it does what it's purpose is we don't need to continue use. Letro and Adex are Type 2 Ai's and the success of those drugs are continigent on the Doses and protocol of which we use them. Once you stop them you expose yourself to an Estrogen rebound. Now having said all of that there are also many other reason to why Aromasin use is beneficial to a Bodybuilder. One is Arimidex/Anastrozole Decreases IGF-1 18% while Aromasin/Exemestane Increases IGF-1 28%. Another is Aromasin is also known to decrease estrogen between 90-95% while boosting Endogenous Testosterone by about 60%, and also help out your free to bound testosterone ratio by lowering levels of Sex Hormone Binding Globulin (SHBG), by about 20% (12)…SHBG is that nasty enzyme that binds to testosterone and renders it useless for building muscle.

This is from a yellow sticky in the PCT forum.
Like anything else, AI preference varies from person to person. Some love Aro and others Adex. Can't hurt to have both on hand and see how you react. Most start at 6.25 mg per day and Aro and go from there.
Also, use the search function above (magnifying glass) and search some of this out. There are many great posts that can help you make your decision.

Pros are that e2 rebound won't take place when you stop taking it.

Cons are that you have to take it more frequently (Ed to EOD)

Use the blue magnifying glass up top and research them. There are a bunch of posts on it. It's basically up to you which to use. I would get both and try them out and see what you think. You could feel better on one and not the other. Aromasin has a shorter half life. Doses range from 6.25 mg - 25mg , depending on how gyno prone you are. Most run it daily or Eod. Tiral and error to see what works. Start off low and raise if you need to. The same with your adex. I'd start .5 e3d. Then .25 eod if you had to. .5 eod might lower your e2 to much.