be a matter of opinion

To be a topic that is subject to one's preferences, as opposed to a verifiable fact. I know it's a matter of opinion, but I think that living in the city is more enjoyable than living in the suburbs. A: "Ew, how can my blind date like the Yankees? They're the worst!" B: "You do realize that's just a matter of opinion, right? And one coming from a diehard Red Sox fan, no less!" This is not a matter of opinion—you have to take these courses to finish your degree. The department head told me so herself.

be a matter of oˈpinion

be something which people disagree about: ‘She’s a great singer.’ ‘That’s a matter of opinion’ (= I do not agree).