both of these drugs work in a similar way, both can and will cause rebound issues if not used correctly. i dont see how comparing them will help. letro is much more aggressive at what is does and needs to be approached easily and slowly, it can and will crash your estrogen fast and hard, you dont run it long, i have seen some use it for an AI, i dont get it, but if it works and it works effectively than good. but i would only ever recommend arimidex for on cycle AI and letro for a gyno treatment. letro can be difficult to dose for some, some it can shut down estrogen with a very small dose, i mean well under a half miligram and others need more, so the predictability of letro dosing can be tricky and needs to be ran more frequently than anastrozole. which is typically every 3 days and for some even dose farther apart. they treat the same thing (estrogen) but there uses are very different or at least should be viewed that way. even though they can be used the same its not often what we do with them.

so the break down is,
anastrozole- less frequent use, easier to dose, less likely to crash estrogen, primary use is on cycle AI, likely estrogen rebound issues.

letrozole- more frequent use, more difficult to dose, likely to crash estrogen, most common use is gyno treatment, can be used with great care to for on cycle AI. likely estrogen rebound issues.

Personally I like Letro for reversing or bringing down estrogen if it was allowed to get to high. Arimidex is great for being proactive to preventing estrogen related sides, but in my experiebce if gyno symptoms or serious bloat crept up use letro not adex.

I ran a long cycle once and after I came off and went into a cruise at 300mg ew unexpected travel came up for my work. I traveled but got extended and stuck there for an extra week. In my hurry I only brought enough adex for the original amount of time. Long story short I returned and my nipple got sore/itchy but I had started adex when I got home. It didn't have a fast enough effect. Got blood work and estro came back in the 80s. I immediately dropped adex and started letro @ 1.5mg ed. got my bloodwork done 8 days later and letro had brought it back down to the high teens (18 i think). Once it was in control I went back to adex at .25mg m/w/f to keep it there.

that's my experience if you got questions let me know. I get constant bloods so I can get an idea on how doses effect me.