example: http://www.streaminglearningcenter.com/articles/ogg-vs-h264-...
Theora has also suffered somewhat from not being developed through an open process: On2 code-dropped one of the older propritary formats that they were uninterested in supporting anymore, and the Xiph side (which previously had just done audio) picked it up, formally specified it, and radically improved the implementation (of both the encoder and decoder) while retaining compatiblity.
Codecs thrive on network effect-- you might be happy to take some efficiency loss for improved licensing terms and patent assurance, but there are plenty of other who don't care (or at least won't care until the lawsuit arrives on their desk). It's not good enough to be very good in one dimension, to be wildly successful a codec needs to be great in many dimensions; a decade ago you could argue that Theora was in that space (and I did!), less so today.
... and wildy success is itself the ultimate performance objectve, not for the sake of the egos of the developers but because only though ubiquity do codecs stop being an issue that people trying to deliver great works have to worry about. 99.9% of the time an application developer is not thinking at all about what his TCP stack is doing, who made it, or what its settings are-- ultimately that kind of effortlessness needs to move up the stack in order for the world to move forward.