This type of discussion is covered in
this thread.
Just be warned - you'll hear earful of error corrections on the points you made in your post.
No preference for the container used for divx/xvid? We do have preference. Those are usually mkv or avi these days. OGM is hard to come by anymore, because of the limitation the container has. You don't want to see xvid in realmedia container, do you? You don't see it in asf container? "Any container" opens up too big of a door for any obscure containers out there. MP4 container can be used for this as well, but hardly anyone uses it for xvid.
And I still fail to see why you prefer mp4 over mkv, especially for current fansub releases. It's not like you can take any of those mp4 releases to portable devices like iPod or PSP - the video encoding specs used far exceeds what's allowable by those players. To make the video compatible, you'd have to reencode them yourself. At that point, having mkv or mp4 as the source wouldn't matter at all. (The only reason might be some proprietary software only allowing certain media types...)