Well it all depends on how much bitrate (filesize) you're willing to spend on each movie which controls how crappy the quality will be.

In my opinion divx isn't a good backup codec to use. It blurs and unsharpens the picture.
That's why xvid is mostly used in the piracy circuits.
It's sharp and delivers crisp picture.
So I'd suggest you use that one or the H.264 tech.

The program Wharry suggested has output support of both H.264 and xvid.

So try it out