If you have a hopper I would do mornings and evenings at DL and mid day at DCA. If you just have one day tickets to each park- its a toss up! Saturday will likely be busier at DL, but it also has longer hours that day, and the fullest entertainment schedule. Giving you the most 'bang' for your buck. But if you dont like crowds, I would would do DL on Sunday and DCA on Saturday.
I agree with the previous poster... Saturdays are always the best for Disneyland because you have more to do and longer hours to do it in. Sundays at DCA will be more kick back.
If your not too into the crowds then definately wait until Sunday for Disneyland.