Just to reveal my actual feelings on the subject, I tend to think that Y is strictly correct in both cases, in that X really can't perfectly know what they're missing out on, but that X is justified in choosing not to find out. In the alcohol case, I am typically X, and in the meat-eating case, I make an effort to avoid acting like Y.
I feel like I'm merely believing in the possibility of (not) enjoying an action for reasons that are strictly disconnected from the experience of the conqequences action. A person might well like the taste of meat if they actually tried it, but doesn't like the fact that that experience comes at the cost of an animal's life. I might very well enjoy the experience being drunk, but I don't like the idea of alcohol making me so.
I think the argument that "they are not analogous because alcohol is intrinsically social" doesn't work at all. First, I don't think vegetarianism is totally irrelevant to socialization, even though I admit that it's probably much less central than alcohol: Have you never wanted to go to, like, a steakhouse and had vegetarian friends in tow that vetoed it?
This isn't to say that you aren't justified in trying to persuade people to start drinking so that you can socialize with them more. I'm not trying to rail against people that do that to me: I do understand that it's in their own interest, not too different from trying to convince me to start swing dancing or something, another thing that falls on my deaf ears pretty often :) I'm just trying to decide myself whether not drinking is a ridiculously irrational decision, and this analogy feels like it's convincing me that it's not necessarily ridiculous.
I remember yishan made some post some time ago about analogies not being able to prove anything, I think. I agreed with it at the time, but I feel like in this case, an analogy has concretely helped me think about something. I am having a horrible time to try to describe why it feels like legitimate argument, though. Maybe it is simply not. It feels like it hinges on which differences "count" between meat-eating and drinking. Of course there are going to be differences, but now I don't know how to specify why I feel I can rule out camille's "intrinsically social" objection. I'm ready admit that alcohol is more intimately connected with socialization somehow, but I want to say that that fact "doesn't break" the analogy I'm trying to make. Hmm.