Hi FW...  in all honesty, I don't think there is a great deal of difference in treatment effectiveness between the two drugs.  Being post menopausal would mean that Anastrazole is the drug you would be prescribed and the drug with a marginally increased success rate I would imagine.  The only person who can really advise you and help is your oncologist.  Can I suggest that you have a lengthy chat with her/him in the New year and get onto one or other of the drugs for the duration asap.  The main thing is that you take a hormone suppressant to stop disease progression. Please do that and keep well.  Happy new year! X