Is there an actual HTML5 standard from either of them that you could point to and demand compliance to? It seems apparent that WHATWG doesn't even consider that a desirable thing so we can safely forget them, but just how much longer does W3C plan to dink around?
But even then, is there even one browser that is or will be 100% compliant to either spec at any moment in time? Unless there is it is again pointless. The whole idea of a standard is that one can take it, create content that adheres to it and expect it to display across a wide range of devices. Is that likely? Nope. So it means browser checks and constant tweaking forever and the only 'html5' apps likely to ever exist will be Metro on Win8 because at least it will be a reasonably stable target in wide deployment. Bah.