I personally found it a bother that there seemed to be some kind of rule that if you were singing it, it was ah-men and if you spoke it, it was ay-men, so I decided to always say ah-men in every case.
At least one other person in my parish agrees with me.
I tend to go with ah-men. Formerly I went with ay-men in English, and ah-men in Latin, which I had been taught somewhere along the line.
When I began singing in the choir, I was taught that the “English” way (maybe I should say, the high English way) of pronouncing words was preferable when singing because it has more of a prayerful sense or sound and dignity about it. I’m not sure I’m explaining that right. Before that I always thought of the “high English” pronunciation as put on, snobbish, or affected. But as I listened more to the singing I could see that if it was done well it did lend a sense of dignity. Done poorly, it still sounds affected to me, like someone putting on airs.
Anymore, I listen to those around me, and I go with the majority. Among Franciscans, that seems to be ay-men. Among more traditional or conservative Catholics (not that Franciscans are liberal, but they are more laid back), it’s a mix, but a leaning toward ah-men. In the choir, when speaking, not singing, English, it’s usually ah-men.
I don’t think “when in Rome, do as the Romans” is a cop-out. It makes sense to me to fit into the culture wherever I am worshiping, and not to be a meaningless distraction, as neither way is right or wrong.