I suspect mainly technical. Chromium is already embedded everywhere, Gecko a lot less so (I can't even come up with a single modern example, although I'm sure they have to exist). There's probably a lot fewer resources and support if you decide to go the Gecko route.
I also vaguely remember reading somewhere that Gecko is a lot harder to work with for third parties due to unstable APIs and frequent breakage, but don't quote me on on this.
You're technically correct, because they use Blink, which is a descendant of WebKit.
I'd say it's about as pendantic as insisting that Windows 7 is built on top of Vista as opposed to XP. The prior statement is certainly more direct and strictly accurate, but that doesn't mean the latter statement is automatically false.
I don't know how to respond to this except to say that anyone operating on either the assumption that Chromium uses WebKit or the belief that Blink being a WebKit fork means that it makes sense not to consider them sufficiently distinct is mistaken one way or another.
People will act like the prospect of maintaining private forks of NPM modules is a major crisis, but then convince themselves—or let other people get away with convincing themselves—that 8+ years of diverging development involving two software giants' investments of billions of dollars of engineering resources poured into implementing their vision of what is one of the most complex and complicated undertakings that exists in software development is somehow no big deal.
(And that's not what "pedantic" means. Both this parenthetical and your comment are examples of pedantry.)
I actually agree with you. That probably prompts the question: "how on Earth could you possibly hold both of these stances simultaneously without being a big, fat phony?".
Yeah... okay, admittedly it probably doesn't prompt that question because you have better things to be doing, but I have nothing better to do, so I'll explain myself anyway!
The comparison to 7/Vista/XP was not accidental. As you may know, there is an 8 year time gap between the release of 7 and XP. Moreover, Vista was a huge transitional change. Under the hood, 7 and XP are different animals, even if they do share common ancestry and deliver the same baseline functions.
Taking these things into consideration, it's not terribly pedantic to insist that Windows 7 is, in fact, built on top of Vista and not XP. It's still a hair pedantic, but only in the context of this fact being used to correct someone with a less strictly correct (although, I insist, still true) interpretation. That's the feeling I was trying (and failing) to convey with my comparison, which happens to actually be in agreement with your counterpoints.
> there is an 8 year time gap between the release of 7 and XP
Which is why the metaphor is off. Safari+WebKit and Chrome+Blink are being developed in parallel and competing with one another. They're not two releases in the same product line where one is the dead forebear and the other a successor.
> it's not terribly pedantic to insist that Windows 7 is, in fact, built on top of Vista and not XP
What? That wasn't the topic. None of this is relevant.
The topic is which engine Chrome is using. Explaining that Chrome doesn't use WebKit isn't pedantic. However, when someone does explain it, for someone else to appear and point out that the engine it uses is forked from WebKit—a nugget of information that changes nothing about the discussion—is pedantic.
I think you're responding at this point for the pleasure of feeling like you're having a conversation, or you're still misinformed about which browsers use which engines. WebKit is not Blink, and Chromium is using the latter, not the former. That's the whole point of this entire digression.
I also vaguely remember reading somewhere that Gecko is a lot harder to work with for third parties due to unstable APIs and frequent breakage, but don't quote me on on this.