It really depends. Disneyland is great, just walking down Main Street makes me happy. However, DCA has Carsland, which has been reason enough for many people to schedule vacations to DLR, rather than WDW. I think you may be best off taking a good look at what you would want to do in each park and then decide where you would rather spend your day.
We had just one day last November, but had hoppers. Here's what ended up on our must-do list (BTMRR was closed then; otherwise, it would've made the list):
DL:
Small World
Star Tours
Space Mountain
Haunted Mansion Holiday
Winnie the Pooh
Pirates of the Caribbean
DCA:
Toy Story
Tower of Terror
Radiator Springs Racers
California Screamin'
Animation Academy
As you can see, DL beats DCA for my group, but just barely. We did end up experiencing a few more things, but this was the must-do list that we started out with.