The Rema (583:1) codifies the custom of eating pomegranates on Rosh Hashana as a good siman for the upcoming year, while the Ben Ish Chai (Nitzavim 1:5) says to avoid tart fruits - like pomegranates or grapes - on Rosh Hashana. What do contemporary poskim suggest about eating pomegranates on Rosh Hashana?
I haven't yet found any poskim on the issues, but at least as a starting point, on the Chabad website here it writes:
There is a common practice to eat a pomegranate on Rosh Hashanah, as its abundant seeds symbolize our hopes that we will come before G‑d with abundant merits. Interestingly, the Ben Ish Chai (Rav Yosef Chaim of Baghdad, 1833-1909) writes that on Rosh Hashanah one should eat specifically a sweet pomegranate, and he emphasizes this point several times. Of course, the pomegranates we have today generally have a bitter, pungent taste. It appears that in Baghdad, where the Ben Ish Chai lived, they had sweet pomegranates. In any event, in light of the custom to refrain from bitter foods on Rosh Hashanah, it would seem proper to dip the pomegranate in sugar to at least diminish its pungency.