The very first DivX codec. It still produces very good, crisp picture quality and you can't go wrong by using this codec. You are guaranteed to get good results if you use DivX 3. Even though this codec produces crisp picture qualtiy, you also get more macro blocks.
The latest DivX codec from DivXNetworks and it replaces the old DivX 4 codec. This codec has new features that DivX 3 doesn't have such as bi-directional encoding which results in movies with a smaller file size. It also produces really good picture quality but some say it has slightly blurrier picture than DivX 3 but you also get less blockiness.
This is a new MPEG-4 codec that provides easy 2-pass encoding but might be a bit harder to setup then the other codecs. It is still early in development but I am already impressed the by the results it gives. In my opinion, I find that this codec gives the best results overall as you don't get as many blocks and at the same time providing sharp video quality.