Most of my time has been at WDW and I absolutely love it.
Still, I think I prefer Anaheim.
DCA is my favorite of the parks I've been to. Screamin', Soarin', Muppets, ToT (not as good, but still a fave)... I love the food (and samples

) on the pier, and want to try the winery my next trip.
The MK is the original, and I'm the kind of sentimental sap who can feel something like that. Some of the original rides are better here, and you can tell they are knockoffs at WDW after having seen them here. Pirates - always a fave since day one at WDW - is better here, and I hope one day to eat at the Blue Bayou (dang rehab).
Dining, speaking of the Bayou, I love at WDW. Biergarten is my favorite restaurant in any Disney park I've been to. So many great places to eat, and even restaurants in different resorts which I'd contemplate traveling back to just to eat at.
Also what I like about DL is the non-Disney aspect: You're still in a city, with cheap but nice hotels, and a quick ride by car or bus to things like sporting events, "regular" restaurants, and a not-so-quick ride to one of the U.S.'s major cities and everything that makes SoCal SoCal.