RE: Disneyland or Disney world?
I must disagree and say that MK's version of Splash is better. That said, you can't top DL's Space Mountain and their version of Pirates is so much better, it's crazy.
DCA has been built up to be a good complimentary park to DL. Honestly, it's now a better park than Epcot, DHS, and DAK, in my opinion. Screamin' is a great coaster, Midway Mania actually makes sense with the Boardwalk theme, and that Ferris wheel is so freaking fun. ToT is vastly superior at DHS, but it's still a great ride in California. To top it all off, my favorite of Disney's nighttime shows is World of Color (though I still prefer USF's Cinematic Spectacular).
Yes, everything is so much bigger at WDW, which is an argument I've heard from many friends, but I actually find that to be a bit of a negative. I can easily slow down, relax, and breathe in all that DL has to offer, which is similar to why I have always loved BGW. There are only a handful of attractions across the WDW Resort that are not available at DL, but there are also some attractions unique to DL as well.
I love New Orleans in DL. It's such a great place to stop and enjoy the scenery. The food is amazing. I've never had a theme park meal to top the Monte Cristo sandwich with beignets. Similarly, I enjoy the San Francisco area of DCA; it's quiet with a nicely themed wharf and also has some delicious food available.
Most importantly for me, you can't top the value of DL. I have many times been able to easily enjoy both parks in a day at a much better deal than WDW.
If you're looking to "do Disney," go to Orlando. If you want to have a somewhat different, but just as amazing, experience that won't break the bank, Anaheim wins out.