Okay, so we have two different coasts getting the same attraction, Toy Story Midway Mania. I had the pleasure of riding both, and while the core experience is the same, there's some other minor changes.
The Names The Same: We've got the same marketing problem on both coasts. Nothing in print wants to confirm it as "Midway Mania", just "Mania!".
Both Bring Refinements to their Host Parks: Interestingly enough, at both coasts, TSMM is a 'turning point' attraction, where the budget for the attraction also includes a step forward for the park it's in. At Hollywood Studios, it brings the Pixar Place land, a whole new area. At DCA, it brings a whole new look to an existing land, and the first step for major refinements to a park.
Room vs. Midway - In the Florida version, you are already in Andy's room upon entering the queue. However, in the California version, this is not the case. Both fail at this story-wise. In both, we are the size of toys, but we have no clue how we get to that size, or when the transaction takes place. However, at least the DHS version makes the most sense. The DCA version, has the full size toys among the boardwalk, and just doesn't work story wise. However, I think DCA wins from an overall look perspective, since it's queue and vehicles blend into the Midway/Boardwalk look so well.
Longer is Better: DCA's track is much longer, because of Screamin'. I love the movement of the vehicles, and more is better. While both feature two separate tracks, the longer DCA version creates less 'Hold Time', and a better overall experience.
Overall, I think there is no 'winner'. Both provide a same core-experience, and have their advantages and drawbacks. While I don't like the fact that they open the same attraction in both parks, at least with them being built at the same time, there is less budget to cut on the later built one (see: Pooh, Tower, etc.)