Wanted to reply to this post a bit and to the original post. For perspective, we lived in CA in the mid-to-late 90s and visited DL I believe 3 times and really enjoyed it. Moved back to the east coast in 2001 and have been to WDW 5 times since the move. We are going to DL next month for a very short 1 1/2 day trip (there for business, taking advantage of the park opportunity) and are really excited about the visit but wish we had more time.
So, with regard to the differences (and keep in mind we haven't been to DL in about 14 years) WDW is much more self-contained, which we love. Once you pass through the gates you are immersed in Disney and don't have to worry about the outside world (and can't even see it). That said, it is a BIG place. If you are traveling from resort to a park or park to park it can take a lot of time, especially if using Disney buses. We've had to wait up to 20 minutes for a bus, then you've got anywhere from a 10-20 minute ride, then you've got to walk to the gate, get through security, etc. So make sure to allow plenty of time to get somewhere. We've stayed at Port Orleans Riverside, Polynesian and Yacht Club and the latter is our favorite resort because of the proximity to Epcot and (to a lesser extent) DHS. We love being able to walk to Epcot in 5 minutes. I prefer to take a cab if I have to be somewhere at a particular time and that has worked well for us getting to parks prior to opening (especially AK and MK).
We also really enjoy the table service options at WDW. QS is reputed to be better at DL (and may be) but there are tons of table service restaurants at WDW, some of which are very good. Since you have the deluxe dining plan you certainly should take advantage of signature restaurants -- Yachtsman, Narcoosee's, Flying Fish, and California Grill are all good. For 1 credit table service, Boma is a can't miss and Teppan Edo, Chefs de France and 'Ohana are all good while Be Our Guest has decent food and great theming.
With regard to the parks, DHS is our least favorite park, even though it has two of our favorite rides. Tower of Terror is AWESOME and Rock n Rolla Coaster is good too, though awfully short. We find the rest of the park to be fairly meh, except Toy Story ride, but you can only ride that with a FP+ unless you want to wait an unreasonable amount of time in line. The rest of the park doesn't appeal to us, and the food there isn't particularly good.
I would say that AK is a must-do. The park itself has great theming and as the previous poster mentioned there are some real gems there, including Flights of Wonder, Expedition Everest and the Safari ride. I would definitely hit both of the trails as well. Dinosaur doesn't come close to Indiana Jones.
Epcot is interesting. Very few rides, although we enjoy Test Track and Living with the Land. Tons of pretty decent places to eat though, and it is neat to visit the different countries. We really like Germany, Italy and Mexico. Some of the stores are pretty cheesy, but some are really neat. If you have folks who like adult drinks then Epcot is a must do.
Others have covered the differences between MK and
Disneyland better than I can so I won't go into details, other than to say make sure to arrive before park opening if possible (this is true for all parks) because it gets really busy at midday, regardless of time of year. And Magic Kingdom is really magical late at night when the crowds have thinned a bit. Of the rides/shows there, our favorites are Splash Mountain and Big Thunder and the shows for Monsters, Inc. and Philharmagic. Haven't had the chance to ride 7DMT.
