Since I haven't seen h.264 or this new DIVX codec yet, I can't comment on etheir's quality. From what I gather, h.264 should deliver excellent quality (course they said that about MPEG-4 too). Also, h.264 is very scalable, unlike most other codecs which have sweet spots in terms of size and data rate. So h.264 can just as easily be used for HD video and a tiny little web video. Not to mention full integration with QuickTime, a must. And h.264 has been ratified for use in both Blu-Ray and HD-DVD formats (upcoming).
DIVX can go away any day AFAIC. Admittedly, a lot of DIVX content can look quite nice. I'd just rather see a true open standard take hold (h.264). How's that for a concept? Gee, an open standard supported equally by competing companies. Not since MIDI have we seen that type of cooperation. And yet MIDI is still utterly dominant in the music world twenty years later. OK, now I"m off topic, moving on