Both certainly have their merits...
Short, cheap vacation (2-3 days) I'd go with DL. Compact size, only 2 parks. Don't have to pay as much to stay at a DL property (motels on Harbour Ave. are just fine, never there anyway). CA is a great park for adults, love the wine tasting. Animation building is stunning. MK park is the original. Indiana Jones ride is amazing (better than Dinosaur at AK IMO).
Longer vacation, bit more money to spend, definitely WDW. So much to do and chose from, huge selection of great restaurants, 4 theme parks, plus Pleasure Island, plus water parks, and completely surrounded by Disney 24 hours a day.