Disneyland is my "home" park. Been there at least 30 times, and only been to WDW 3 times. This is how it is different:
A LOT smaller, yet a LOT more attractions (if you are simply comparing MK to DL). Attractions DL has that MK doesn't:
Matterhorn
Alice in Wonderland
Pinocchio
Indiana Jones and the Temple of the Forbidden Eye (Awesome ride!)
Casey Jr Circus Train
Roger Rabbits Car Toon Spin
StorybookLand Canal Boats (a personal favorite)
The original Tiki Room
It doesn't have Buzz Lightyear, the carpet ride and Carousel of Progress/TimeKeeper and any sort of Alien Encounter. In fact, Tomorrowland is kind of in sad shape right now. But I think DL's Fantasyland ROCKS! So does it's ToonTown. They are building a Buzz lightyear ride and Space is down for rehab until 2005!!!
And not just smaller in diameter----the castle is smaller, the buildings on Main St. are smaller...it's not such a huge scale and doesn't take as long to walk from Adventureland to Tomorrowland for example.
There is no Liberty Square, but DL has New Orleans Square which is very pretty.
Fantasmic happens on the Rivers of America and has a few more very exciting sequences.
"Beautiful" (HA) Anaheim is RIGHT outside the park- no miles and miles of landscaping- you got Domino's pizza, McDonald's tacky hotels, liquor stores and 7-11's a stone's throw from the entrance. This is why I like WDW so much- it's truly another world.
California Adventure is right across the entrance- no bus lines to wait in. And it has some fun attractions- Soarin Over California, California Screamin, the River Rapid ride and Tower of Terror opens in a few weeks.
I think some of the rides at DL will blow you away when you compare them to MK- Pirates for example has several more scenes and is just more exciting somehow. Small World has a beautiful facade, not just stuck in Fantasyland like Snow White. Splash Mountain and Big Thunder are slightly different (although I think Splash is better at MK), and Fantasyland has a very old European feel, fantastic attention to detail- your daughter will LOVE it!
Not as many sit down restaurants as MK, but enough variety to be happy. No condiment bars like Pecos Bills or Cosmic Rays either.
I love both parks.....you *might* be disappointed with DL if the size distracts you, but I think you will love it. Plus there is PLENTY to do in So California!