Anecdotally, I think Disneyland appeals more to young children and adults than it does teens and preteens. My daughter is 7 and vastly prefers DL to WDW... less planning, less stress, park hopping is easy, better Fantasyland and lower wait times are her primary reasons. Those reasons apply for me, too, but of course I also notice the better ride maintenance and the superior theming in Fantasyland, Adventureland, and New Orleans Square (as compared to Liberty). However, once families have kids that are a bit older they may be able to deal better with some of the nonsense at WDW in exchange for a greater variety of experiences.