"You aren't in" vs. "You're not in" [duplicate]

Possible Duplicate:
“They are not”: “they're not” versus “they aren't”

I noticed that you aren't in and you're not in are two ways to shorten you are not in.

Are they always interchangeable? Are there situations where you would choose one over the other?

Both mean the same thing. However using you're not seems to me to place more emphasis on the negation in speech because of the solitary not.

Another reason to use you're not would be that the listener would less likely mistake aren't for are in a noisy place for example.

This question has been discussed a few times on various grammar & language websites. At answers.yahoo.com the concensus is:

When expanded, these represent the same words: you are not. In that regard, there's no difference. Keep in mind that neither expression should be used in formal writing because contractions are considered somewhat informal.

At wordreference.com one poster rants against "we aren't, they aren't, you aren't etc.; while another writes: "We're not going stresses the not. We aren't going does not stress anything"; and a third argues by analogy with I'm not being preferred to I amn't or I ain't.

The longer thread of comments at reddit.com seems more useful than the two references already mentioned; it gives several examples are given where one form may be more natural than the other, such as:

a: I'm a computer programmer. b: No, you're not.

a: I'm going home now. b: No, you aren't.

The reddit thread includes examples of different emphases (much as before), and also digresses into inconclusive mention of You'rn't, You'ren't, and shouldn't've.