XVID, DIVX and other video questions

Hi all, just wondering which codec you guys view as better - XVID or DIVX (or any others for that matter)?? I'm currently in the process of converting a few videos/movies/tv shows to avi's and can't work out which codec I should use.. I've seen some pretty impressive stuff come from both ends of the field..

Something else Im curious about is the bitrate... If i set a bitrate of say 1200kbps in VirtualDub-MPEG2, when it's finished, (in windows explorer) I right-click on the avi file and goto properties, then to the summary tab and the bitrate down in the 'video' segment says something like 156kbps or the like... I really don't understand what the difference is (between 1200kbps VirtualDub and 156kbps Windows), I thought one might be talking bits and the other bytes, but I can't work it out...

Also if someone could direct me to a place where I could find a bit out about Quantizers and all the other jargon that I don't totally understand to do with video bitrates, sizes and quality.. That'd be grand...

At the moment Im converting part of a TV series from HDTV to an AVI file, any tips on perhaps some preset quality and size settings for me to use??

Thanks a bunch!