Yes, you can have an opinion on which art is better. You can also argue about which religion is better. If you've never done either, I recommend it some time. Having opinions and forming arguments can be very fulfilling.

I mean, that seems like a kind of important question to me.

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Also, I don't really reject the possibility of there being a fact of the matter as to the aesthetic quality of things.

I don't really affirm it either, and if it is true I'd say it is entirely permissible to have aesthetic preferences that go against the true fact of the matter as to aesthetic quality.

And if it turns out that there is no fact of the matter as to aesthetic quality, then arguments that something is of good aesthetic quality could often be transformed into explanations of why that person has those preferences, which still seems like it could be worth knowing.

So, I think it could make sense to not reject all arguments for a thing being of good aesthetic quality

lots of people have opinions on what art is better. lots of people discuss it. if you don't want to discuss it, don't.