From the above you could see that Flash is installed in most computers. So, if you want your video to be seen by the majority of web users you would want to deal with Flash that allows you to use the V-6 codec and the industry standard H.264.
Or you would opt for Quicktime which uses H264 codec if you’re aiming Mac users.
Generally, the V-6, V-1 and H.264 codecs offer impressive video quality. So, it’s up to choose any of them according to the player you would like to use on your web page.
The point to note is H.264 is processor intensive. So, older computers may not offer a smooth playback even if one quits the programs running in the background. H264 will also not work with older versions of Flash players.
Sorenson Spark is another codec used for .flv files especially in YouTube. If you’re looking for high quality video, you should avoid this codec. Most freeware or entry-level shareware encoders use this codec to encode FLV.
Another point to note is if you would want to your video to be downloaded by users of iPod, iPhone, or PlayStation Portable, you could do well to use the H.264 codec.