The difference is that an exclusive actually does have more news value. By definition, it's news.
delta(P1, P2) is nonzero. Hilariously nonzero. If Steve Jobs had a fit of stupid and had given somebody the exclusive for the iPad, that would probably have been worth hundreds of millions of page views. Page views are, of course, exchangable for money. We build entire industries on that fact.
News media outlets are willing to trade things of value for exclusives. For example, PR flacks value embargoes. TechCrunch will give you one if, and only if, you give them an exclusive, despite their professed hatred for them in all other contexts. That should imply to you that TechCrunch is getting something from the exclusive -- and it isn't delta(N).
Even if your only criterion in deciding what to print was how newsworthy it was, you'd still be more likely to print a story if you'd been given an exclusive.
Also, if you're more likely to print a story when given an exclusive, then newsworthiness is not your only criterion in deciding what to print.
Did I really need to explain that? This reminds me of the thread a few days ago when I had to explain that it was not necessarily meaningless to talk about something that would have happened.
This is why I need to get rid of points on comments. 11 points on a comment makes it into something that demands an answer. Without points it would just have to stand on its own merits.
(Your second sentence is simply false. The newsworthiness of a story isn't constant; it's higher the first time the story is published. E.g. that Steve Jobs had a liver transplant has near zero newsworthiness now, but it was big news when the story first broke. And if someone gives you an exclusive on a story, then you're assured that it will be breaking news when you publish it, with the attendant increment in newsworthiness.)
About my second sentence - I was imagining a story with little newsworthiness, as this is one extreme of your "only criteria". If a publisher is more likely to publish this story because of an exclusive, which is what you seem to be saying, then newsworthiness isn't the only criteria.
I did not mean to be combative or demand an answer from you - my apologies if I came off that way. I just don't agree with or don't understand your point of view, and said so. Apparently 10 other people thought that it stands on its own merits well enough to deserve an upvote. If you don't agree, that's fine, but the snark is uncalled for. If you don't think a post is worthy of a reply, then don't.