Definitely “incomparable” fails to imply “equivalent”. But still, where two options are incomparable according to your morality you can’t use your morality to make the decision. You’ll have to decide on some other basis, or (possibly?) no basis at all. To my mind this seems like an important fact about your morality, which the sentence “my moral preference between A and B is that they’re incomparable” captures nicely.
I think we’re disagreeing only on terminology here. It’s certainly an important fact about your morals whether or not they deliver an answer to the question “A or B?”—or at least, it’s important in so far as choosing between A and B might be important. I think that if it turns out that they don’t deliver an answer, it’s OK to describe that situation by saying that there isn’t really such a thing as your Real Actual Moral Judgement between A and B, rather than saying that there is and it’s “A and B are incomparable”. Especially if there are lots of (A,B) for which this happens (supporting the picture in which there are great seas of weird situations for which your moral intuitions and principles fail, within which there’s an island of “normality” where they are useful), and especially if the way it feels is that you have no idea what to think about A and B, rather than that you understand them clearly and can see that there’s no principled way to decide between them (which it often does).
Definitely “incomparable” fails to imply “equivalent”. But still, where two options are incomparable according to your morality you can’t use your morality to make the decision. You’ll have to decide on some other basis, or (possibly?) no basis at all. To my mind this seems like an important fact about your morality, which the sentence “my moral preference between A and B is that they’re incomparable” captures nicely.
I think we’re disagreeing only on terminology here. It’s certainly an important fact about your morals whether or not they deliver an answer to the question “A or B?”—or at least, it’s important in so far as choosing between A and B might be important. I think that if it turns out that they don’t deliver an answer, it’s OK to describe that situation by saying that there isn’t really such a thing as your Real Actual Moral Judgement between A and B, rather than saying that there is and it’s “A and B are incomparable”. Especially if there are lots of (A,B) for which this happens (supporting the picture in which there are great seas of weird situations for which your moral intuitions and principles fail, within which there’s an island of “normality” where they are useful), and especially if the way it feels is that you have no idea what to think about A and B, rather than that you understand them clearly and can see that there’s no principled way to decide between them (which it often does).