AVC offers much better compatibility across encapsulation formats (notably MPEG-TS) and playback devices than WebM currently does. The Ubuntu community is not going to take care of the surge of support request and bad publicity a new version of VLC gets if it breaks that compatibility.
VP8/WebM is supported, but I do not believe it would an appropriate default choice at this point in time.
AVC offers much better compatibility across encapsulation formats (notably MPEG-TS) and playback devices than WebM currently does. The Ubuntu community is not going to take care of the surge of support request and bad publicity a new version of VLC gets if it breaks that compatibility.
VP8/WebM is supported, but I do not believe it would an appropriate default choice at this point in time.