In just the one day I did Disneyland proper last week, I saw lots of cool character interactions where you'd see Mary Poppins and Burt simply strolling along Main Street, talking to kids and signing autographs. No big fuss was made, no handlers were roaming, it was very natural. Peter Pan is great and always running about in Disneyland. I caught Alice taking a spin on the AiW dark ride, etc, etc. It just makes for a better experience... I would never wait in long lines to meet characters at WDW, but I got several pics with characters at DL simply because they were out and about with no lines.
The characters roam so much more free and it's much more like you've stepped into a living, breathing storybook at Disneyland Park. DCA not so much. They also run the double deckers and the main street cars most of the day there unlike WDW which only runs them in the morning.