I've been told directly by multiple Angular team members that over 70% of Google apps uses Angular in some fashion.
They have said the usage of Angular off of HEAD of master publicly in the past as well, but I don't recall off the top of my head where they have said this.
Well, this thread definitely shined some new light on the area for my. I was actually under the impression that Angular (at least 1.*) wasn't really used within Google. I guess I'm just that stupid and naive.
Yeah I think that's the key difference: the size of the production apps. Though to be fair, Angular is a much bigger part of the front-end stack than React and not something that would be feasible to retrofit GMail/YouTube/etc. with.
