There may be a fair amount of cloning between the resorts, so if you're going to DLR just for completely unique attractions your going to be disappointed. With that being said I would say that each Disney Park has its own unique attractions and that California Adventure has more unique attractions than any other than Disney Park save for perhaps Animal Kingdom. For unique attractions, I like to say that Grizzly River Run is a first class rapids ride, and that Hyperion Theater hosts a stage show unmatched (in production value) from anything at WDW. If you're into meeting characters and make the effort, you can often spend more time than just a quick photo. A personal favorite of my mother's is to watch the Boudin Bakery sourdough bread loaves being made and then order a clam chowder sourdough bread bowl from the restaurant next door. As a Californian, when I visited WDW, I didn't avoid duplicate attractions, I just made it a point to hit every unique attraction at least once during the trip and had a great time! For WDW regular's, I recommend the that they tour with the same mindset.
p.s. Knott's Berry Farm is literally in the town next door and is worth considering as an unofficial 3rd gate.