Which is the better medication to be on following a heart attack: a beta blocker or an ace inhibitor?

I am 37 years old and had a non-specific heart attack. My cardiologist and a second opinion cardiologist both agree i should be on Lopressor and Norvasc. I was sent to a workers comp. cardiologist because my MI is considered to be job related. He wants to place me on an Ace inhibitor instead of the Lopressor.