Taste is personal. I recommend you try different origins and blends and also try different roasts. Light roasts tend towards sour. Dark roasts tend towards bitterness. Medium roasts are most popular. Medium roasted beans are about the color of milk chocolate.
So called "espresso" beans are often misnamed. In most of the world "espresso" has become a meaningless word for coffee. But in Italy espresso blends are mild because Italians drink espresso straight. The AeroPress is already mild. So brewing Italian espresso blends in the AeroPress might tend towards flat. But, of course, taste is personal. My current favorites are medium roasted Yirgacheffe beans and medium roasted Guatemala beans.