I think that DCA, in general, will be the most surprising to you. I'm not even singling out one thing or another thing (several new rides and attractions have been added over the years to both parks), because there are lots of new things. But, in the past, even though I had grown to really like the previous version of DCA, it was lacking a lot of little (what I call) 'kisses of magic' here and there. It didn't feel tremendously in line with Disney in some areas of the park, and it just seemed to be missing something. It didn't have a heartbeat to it, really. It didn't particularly evoke any specific feeling or memory or emotion. It didn't tug at the heartstrings, with perhaps an exception made for Soarin's majestic scenery footage. DCA didn't even feel particularly creative or imaginative.
Somehow, with the inclusion of Cars Land and Buena Vista Street -- both of which are incredibly themed and detailed lands in their own ways -- DCA now feels like a more cohesive, imaginative park. Those two new lands somehow managed to make all of the other lands in DCA feel more like Disney! They helped to connect the dots. For example, Buena Vista Street (which is now the emotional, nostalgic epicenter of DCA, like what Main Street is to DL) and Hollywood Land complement each other well. Kooky Cars Land seems to make sense being so close to whimsical A Bug's Land -- I don't know why, but it does. Grizzly Peak is now getting more involved too. Toy Story Midway Mania seems to fit perfectly in Paradise Pier. Pacific Wharf even seems to have more relevance and personality now, and no longer feels like a complete waste of space.
I don't know how it happened, but the whole layout and make-up of DCA makes more sense now, ever since those two lands were added in 2012, and feels as though it is a Disney park through and through. There is still a lot of potential, and a lot of work that should be done to build up DCA even more. But before 2012, it was a park that people didn't know if they should visit or not. It was an option only if DL got too crowded. And now DCA is a destination in its own right.