For Fox and Warner titles, it's definitely better to buy the double disc versions. Lately, for Fox blockbusters, it's better to wait a few months after a single disc title is released, 'coz that studio has a habit of releasing more definitive, multi-disc versions of the initial releases (E.g. Titanic, Ice Age, X-Men). As for Warner classics, it's definitely not advisable (if you don't want to double dip) to buy single disc titles, because these get re-released as multi-disc titles (Wizard of Oz, Gone With The Wind, Ben-Hur, and possibly a 4-Disc Casablanca in the future). But hey, if you really really can't wait for that re-release, and you've got enough moolah, then by all means, double dip if you must!