I go to DL regularly & I just went to WDW for the first time this summer, so as far as what to ride that is different...
At CA - All of Cars Land, best ride is Radiator Springs, similar to Test Track but with the Cars theme, California Screamin', Mickeys fun wheel, Monsters Inc, Goofys Sky school, the Golden Zephyr. There is a QS Paradise Cafe that serves clam chowder in a bread bowl among other things.
At DL - Indiana Jones, Matterhorn, Mr. Toads Wild Ride, Alice in Wonderland, Snow White, Storybook Canal, Finding Nemo Sub, Sleeping Beauty Castle instead of Cinderella castle. The rides that are basically the same but the DL version is way better are Space Mountain & Pirates. Haunted Mansion, IASW, Peter Pan, & Jungle Cruise are also slightly different. The QS we like is the Plaza Inn for their fried chicken meal.
If you are interested in checking out my new blog I have some posts about our visit this summer to DL/CA with lots of pics - jensjourneys.com.
Have fun!