We've pointed out previously that your mp4 number is wrong and your conclusion about Ogg overhead is misleading at best. Directing you again to http://lwn.net/Articles/377928/
For illustrative purposes, at that comment you'll also find an Ogg file that we repacked with the same overhead as the mp4. In addition, the most recent release of libogg (drop-in upgrade) reduces default overhead of Ogg-framed video by about 35%. In the grand scheme of things, that means it reduces the overall rate of a bitstream by about .38%. Personally, I think it's almost a misplaced optimization. I'd rather be looking at much larger wins in Vorbis or Theora or CELT. For example, the new libvorbis reduces 5.1 surround bitrates by 10-40%, which is between 25x and 100x more savings.