DD is 11 now, and we've introduced Harry Potter, so on our DLR trip we spent a day at Universal Hollywood as well. I know it's different than Orlando, and we will still go to Orlando - but, overall, Disneyland was still a better experience. The layout of Universal Hollywood (with the multiple escalators to get from the upper lot to lower lot) didn't help. Super Mario World was okay and well themed, but DH and I didn't enjoy the MarioKart ride as much as we were hoping to. We couldn't get into the quick service location there at all (virtual queue for it and we were shut out basically right after opening). The powerband was interesting, but even that was sadly difficult for DD to access due to the force required for it to interact with the bricks. Harry Potter was the biggest hit by far, so I assume diagon alley will be also.
If we head out to DLR again, I don't know that we will bother with Universal though.