I can't say one is better than the other.
I really enjoy them both, for different reasons.
The reason I love WDW...there's so much happening, and so many different things to see and experience. It's sensory overload at it's best. I love that there are several parks, and each has it's own theme and flavor. And I love the themed resorts.
The reason I love DL...you can still see some of Walt's hand in things. It's like his genius is personaly embedded in several areas and attractions, and that is just a cool feeling.
Plus there are several attractions done better, or more unique in DL.