The funny thing is that the "RAWR NO SAFARI, ONLY CHROME!" people don't seem to realize that both are WebKit at the core. Sure, some features are in Chrome first, but that's only because Apple is very cautious when releasing the new features to the general public.
That's because Apple's TOS only allows their system build of WebKit in approved apps, so Google can either use approved WebKit or they can go sit on their thumbs and spin. It's not a voluntary act on Google's part; they would use Blink if Apple allowed it.
Sort of, they're very similar still. In actually the layout is almost exactly the same, its the rendering and compositing that has significantly changed between the two.
Google cannot innovate with Chrome for iOS the way they have innovated on other OSes. All iOS browsers are competing only on the UI layer. Fixing missing web standards or inventing new ones is not possible.
I can't edit my comment for some reason, but as thefreeman pointed out in response to agildehaus' comment, I was referring to how the iOS Chrome is still WebKit.
