> The only operative difference between the two codecs is that WebM is free.

by moving many features of the codec into postprocessing, the video format becomes scalable; a decoder can do “less work” while still playing back the file, albeit at a lower quality. -- http://x264dev.multimedia.cx/archives/292

I have naively taken that to mean that the trade-off of resolution for battery life can be handled in the decoder; that fewer encodings need to be stored on the server to target the same wide range of devices, vs. h264.

I would love to know whether this is true, and what other practical differences there are between the two codecs from the POV of content producers.

edit: VP8 ... Technically, it produces output on par with H.264 High Profile, while maintaining a low decoding complexity on par with H.264 Baseline. -- http://diveintohtml5.org/video.html#vp8