Well as I say, to each his own. I myself prefer 1 CD rips because it is much more professional if you can get a great looking 1 CD rip.
What it all comes down to is personal taste of course, but I say any rip where the movie duration is over 1 Hr, and 50 minutes, I'd have to choose 2 CD rip.
However, if the movie you are ripping is a fairly dark movie (for example, pitch black, which is roughly a 2 Hr movie), making it a 1 CD rip will look very good.
There are 800mb cd's on the market these days, which gives a tad more space for your not so average rip (ie, a movie over 90 minutes).
This of course, is all based on the assumption that you have a competent understanding of the way DivX codec works.
Take care pplz.