The current performance of h.264 vs Ogg Theora is only part of it. Nowadays most advancements related to video compression are patented, simply because the time and effort to make a meaningful advance demands compensation. Ogg Theora, by charter, can not take advantage of such advances. Thats part of the concern: that in mandating its inclusion, it would effectively freeze web video compression to today's state of the art. - DGentry

Mandating inclusion does not necessary exclude the addition of future codecs, does it? Either way, freezing is better than having a mess of incompatibility that renders <video> completely worthless. Thusnelda does appear to have much better compression quality than FLV anyway. - i80and

You're right that it doesn't exclude additional codecs... but if the mass of web sites exclusively use Ogg Theora because it is the safe choice, the presence of other codecs wouldn't be relevant. I do agree that Ogg Theora should have been made mandatory, I suspect that most large sites would implement format detection anyway and serve up h.264 (or the mythical future codec) when available. Nonetheless the arguments made against the inclusion of Theora do have some merit, and they carried the day. - DGentry