I disagree. I think given the choice to do only one thing out of the two, browser vendors should focus on things that fundamentally improve users' experiences with what they already have than implement random specs. I think the lack of canvas is disappointing too, but I think if the IE folks had decided to implement Canvas but not use Direct2D I'd be much more disappointed.

(Of course, you could be awesome like Mozilla and do both, but that's a different matter.)

This difference of opinion is exactly why the argument is invalid unless engine A is strictly better than engine B. WebKit is not strictly better than IE9 Trident.