Bellefan66 said:
We've been to both,and being on the east coast as well,we are HUGE DW fans

. I would ONLY go back to DL if I were visiting relatives.I wouldn't pay to fly there JUST for DL

. It's just not the same. The atmosphere is different,of course the park is much smaller,and you can't count on the weather. Can you tell,we are HUGE DW fans. Good luck on whatever choice you make.In the end,it's still Disney!
OK, I have to say something. You can't count on weather??? What the heck? What kind of freak weather happened to make you say that? Southern California is known the world over for having nearly perfect weather. It almost never rains and if it does rain it is not a down pour... Flordia has unperdictable weather. In California the joke is the weather men can tape a weeks worth of news casts at a time because the weather is so very perdictable and stable. Have you ever seen the movie "L.A. Story"?
Now to the OP- Whatever park you first visited will hold special memories for you. Most people strongly prefer their "home" park. We love both, but I admit DL is my 'home' park, the one I grew up in.
Disneyland is the original and for us that has meaning. Walt walked these streets, slept in this park, and if the magical details are your thing Disneyland has more. As for the castle thing, I think the castle in MK is no where near as magical as the one in DL. It tries too hard to be a "real" castle (and fails). The one in Disneyland is the icon of Disney for a reason. It is fairytale like and sweet. Bigger is not always better.
Disneyland is more limited than WDW, nothing like the AK or EPCOT WS. No full resorts like WDW has (Grand Californian is great, but not the same as the Poly...) What it does have are the rides. It has more rides in less space than the MK, hands down. It has better versions of rides (Jungle Cruise and POC come to mind and now Space Mountian too). It is easier to tour. Oh and the fireworks. You would need to go to Japan to beat the ones in Disneyland. That is always what hits me at WDW, the feeling that they are a good decade behind what DL is doing.
WDW has the resorts, it has the water parks, it has my all time favorite place- EPCOT WS. It has beautiful landscaping. It gives you the feeling that you are really in another world. It has a size and scope DL will never match. The DTD area in WDW is bigger and better and has DisneyQuest which your son might enjoy.
WDW beats DL for onsight food, but DL is not really trying. Southern California has some of the best dining in the world. Since fewer people stay onsite in California there is less need for on site dining. You can go to the real Brown Derby in California.
Either is a great choice, neither can be done correctly in four days unless that does not include travel days. We find it much more expensive to visit Disneyland. Disneyland has record breaking crowds this year too- which is not a good thing in my book.