Gotta say tho, now I'm not sure I understand what "structural difference" is, so this is probably a good time to learn. They're different genres. The singing is the same melody in both, but there's very few similarities between the instrumental parts imo.
I would say this is a good example of Orian's "structural difference vs instrumental difference" comparison. Genre difference on its own is only an instrumental difference. Like you say, the vocal melody is exactly the same, and the structure of the whole song is more or less the same. There's a bit more instrumental riffing between the verses in Britney's version, but I don't think that's very significant.
50 editions since NSC 130 hasn't passed yet tho,180 will be the 50th, so I figure this wouldn't be allowed until NSC 181?
Yeah, this too.