We don't really want anybody to leak anything they personally find interesting, but we do want (good) journalists to be able to discover important stories.
* Some stuff got published that was important and vital (though its impact on public policy was ultimately minimal).
* Some stuff got published that simply shouldn't have been leaked --- for instance, details of technical implants useful only in narrowly targeted espionage.
* Some stuff didn't get published that should have been --- for instance, in light of what we later discovered about Juniper/Netscreen, had everyone to do this earlier, a list of vendors impacted by VPN implants would have been helpful, and could have been doable.
* Some stuff got published that were simple false, such as the notion of a "PRISM" system that gave NSA direct access to Google's systems.
A more carefully curated, competently explained process of leaking could have improved all these outcomes, and that's exactly what Gladwell is suggesting Ellsberg accomplished that Snowden didn't.
Both were imperfect people in unique situations, but Gladwell's distinction seems to boil down to "Harvard, game theory, & Nobel prize winning PhD advisor" in the case of Ellsberg vs. "community-college dropout" in the case of Snowden, followed by Gladwell falling over himself to redefine "insider" right after spelling it out in detail with the language of class, prestige, and societal privilege.
I don't think Gladwell understands enough about either person - or "leaks" in general - to draw meaningful conclusions.
Here's the thing, though: Gladwell is probably not wrong about this. Ellsberg was far better read in to the program he leaked about that Snowden is to the topics of his leaks. As you can imagine, most of my industry friends and acquaintances are broadly pro-Snowden, and an argument that I've seen from literally none of them is that Edward Snowden had the technical expertise to either vet his documents himself, or to build a process whereby they would be effectively vetted. Which you can see by the shitshow that was the original PRISM disclosures.
Another potentially self-serving issue that Gladwell conveniently glosses over in this piece: We could also make the argument that Ellsberg also had a much more effective and courageous press and educated population behind him. But it's easier to smear community college drop-outs and discuss a hypothetical "Edward Snowberg" than a hypothetical New Yorker with more reporters like Jane Mayer than commentators like Gladwell.