I had read somewhere that it takes a while for Letrozole to get up to suitable levels to be effective, whereas Anastrozole packed a punch immediately.
But, I also read in another study that Letro had favorable effects on IGF levels, whereas Anastrozole dropped them.
I use Letro much more than Arimidex, but I just ran out of it, so I just switched over to Arimidex.. which you can do, as it has immediate effect.. but you can't do the opposite without risking a mild break of effectiveness inbetween.. blah blah blah..
I think if you weigh the pros and cons, and then juggle the efficacy of it... throw in some pepper and tabasco..then Letro wins. :duel: