OK, let's compare some major differences between the 2 properties.
WDW is bigger, more Theme Parks, Water Parks, more Hotels, and a variety of price ranges. (So usually a longer visit).
Disneyland has only 2 parks, 3 hotels, basically priced in the "Expensive" range most of the time, and that the majority of guests either stay at a Good Neighbor Hotel or is a same-day visit.
WDW wants to trap people on property, and even offers a free "Magical Express" Airport Bus to get guests to not rent a car.
Disneyland has a deal with Coach USA for an Airport Bus, but it is not free.
While both Orlando and Anaheim have many non-Disney Theme Parks and other Entertainment choices nearby, access in Anaheim is a LOT easier than in "Lake Buena Vista" (aka WDW property).
As Al Lutz mentioned today at MiceAge.com...
MiceAge.com - A different look at Disney...
We'd mentioned before that the online registration for free birthday admission was blowing past all initial projections by the hundreds of thousands. That has continued for Disneyland early in the campaign, while Walt Disney World has seen far less demand for the birthday promotion. The use of the free tickets to upgrade to Annual Passes also has TDA pleasantly surprised, yet at the same time is causing many TDA planners to worry they may soon have too much of a good thing. The problem with rising AP numbers is that they use the Resort facility in a much different way than the average tourist family from Seattle or Sydney. The average AP only visits the Resort for three or four hours, and spends far less money on food and merchandise than their tourist counterparts who typically stay in the parks seven or eight hours per day.
Basically, Disney makes a LOT more money on an average guests stay in Orlando than in Anaheim, and why Disney promotes WDW a lot more, and in the majority of the nation instead of Disneyland.