Tamoxifen or AI?

Next week, I will be seeing my onc for a three-month check up. I have been on tamoxifen for two years, and at that time we will be discussing whether or not to switch to an AI. I have been menopausal (chemo-induced?) since April '06. My question is, what are the risks/benefits of switching to an AI--specifically Exemestane (Aromasin)--from Tamoxifen? I seem to be tolerating the Tamoxifen fairly well, the main side effects being hot flashes and mild nausea. Can you offer any thoughts/advice? I would prefer to stay on Tamox., providing it would be as effective as Aromasin.
I was peri-menopausal at age 46 when dx'd in Dec '05 with IDC, Stage T2N1, PR+/ER+/Her2+++. Treated with mastectomy, AC/Taxol chemo, local radiotherapy and Herceptin, then started Tamoxifen Nov '06.
I do understand the difference between the two hormonal therapies, as well as potential side effects. I just wonder if staying on the Tamoxifen the full five years is a good choice? Or if there is actual benefit with AI?
Thanks for any input.
~Karen~

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A related discussion, tamoxifen and hot flashes was started.