While the true quality of a video isn't as easily measured as some of the other comparison criteria presented here, it is certainly one of the most important factors in the debate over which codec should be preferred for use with the HTML5 video element. Nevertheless, here is are the two main observations I have after using both codecs through Firefox and Safari:
- MP4 is slightly higher quality than Ogg. See the comparison below.
- Ogg tends to look too dark, and in most cases the extra contrast emphasizes picture imperfections.
- Ogg Theora is smaller than MP4, so it requires less bandwidth to stream.
- Ogg tends to get messed up more often when streamed data is erroneous. This is an annoyance when watching content over a WiFi connection, particularly on shared and public networks.
Ogg VS. MPEG-4 Picture Quality
Below is a comparison of the same frame encoded in Ogg Vorbis and MP4:
MP4 vs Ogg Side by Side