to be honest with the price of compact flash cards nowadays card space shouldn't be an isssue
the only advantage would be in continuous shooting ( more frame per burst ) but thats where it ends really
i can see no other advantage of using the smaller raw settings in fact over the time i have owned a 50d ( from launch ) i have never used anything but 15.1mp raw i don't see a reason to use the others
when i read this post it reminded me they have other raw settings i'd completely forgot about them
