Disneyland is by far the superior park - everything about it is just magic, from the layout to the rides to the decorations etc - the park itself is the attraction and the rides are a bonus.
DCA is, at first look, a disappoiintment, it looks like every other theme park you've been to. But it has great rides - especially California, Soarin, Grizzly River Run and Tower of terror.
A pass to hop between the two parks costs about $20 more and in my opinion is worth it.
Don't spend long at DCA just get the three rides I mentioned above, and spend the rest of the day in Disneyland just soaking up the atmosphere and taking a few of the better rides like Indiana Jones, Splash Mountain, Peter Pan, Pirates, Haunted Mansion, and if time permits, Big Thunder, Pooh and Matterhorn.