> Adding a new browser will just increase the attack vector.

More potential ways to attack? Sure. More actual attacks in practice? Not necessarily.

Let's imagine we have a hypothetical 100% secure browser, and we can get people to use it 50% of the time on on iOS. Then 50% of potential attacks become impossible. It doesn't matter that vulnerable Safari is hanging out in another part of the OS if attackers can't actually get their code to run in that context.

Except you ignored my second point which is the browser is in use throughout the system anyway. Yes it would be less likely to attack but still possible. Also a 100% safe browser does not and will never happen.

I didn't ignore it, but perhaps I wasn't clear. My point is that if Safari is in use throughout the system, but used, say, 50% less often (vs. a hypothetical 100% secure browser), then 50% of the time attacks that were previously feasible become infeasible. Frequency / probability of usage matters, not just whether something is installed.

And yes, a 100% safe browser is a fiction (thus "imagine" and "hypothetical"). But I think it's possible that another browser could be vulnerable to fewer attacks than Safari.

I think we're in agreement: adding a new browser increases the number of vulnerabilities that could potentially be exploited (assuming the new browser isn't 100% secure, which will always be the case in practice). And at the same time, moving some usage to a more secure browser makes attacks less likely in practice. I think the latter is more important than the former.

> Yeah, that’s a good thing to prevent browser monopoly.

What a joke. You're cheering for monopolistic behavior while claiming to be against monopoly.

Its the same logic as "Yeah, get those _bad_ immigrants out. I'm one of the good ones"

Absolutely not. Currently the only thing preventing us from having a “chrome is the internet” situation is because WebKit is pushed. If WebKit was the only browser I would not say the same.