"Which is the most bitter wine?" and "Which wine is the most bitter?" are different questions. Imagine there are two boxes which you can't see through, and one of them has the bitterest wine in it and the other has the sweetest honey. Now you would ask "Which is the most bitter wine?", but not "Which wine is the most bitter?"
That possibly depends on where you're from. Personally I prefer most bitter.
But in the context where you are in a place with lots of wine, it's okay to say both "Which is the most bitter wine?" and "Which wine is the most bitter?", right? I think both will yield the same answer. I also think that most people would think of this specific situation when translating this Korean sentence into English which would probably get them (including me) wrong.
But I think I now understand that those two should be structured differently simply because of your given situation. Thank you for that!