The Wonder and the Magic are basically identical in design. The only thing that differs is the name of some of the restaurants/bars.
The April 27, 2013 cruise is on the Fantasy, which is a whole other story.
It is about twice as large as the Magic/Wonder. We have been on the Dream which is the same size as the Fantasy. There are quite a few differences between the Magic/Wonder and Dream/Fantasy. However on all of the ships, the pools are smaller than what is needed for all of the passangers, which doesn't bother us because we don't use the pools onboard.
There is a different "feel" between the smaller and larger ships, and it takes longer to walk from place to place on the larger ships as would be expected.
But personally I like both the Wonder and Dream and don't have a preference for either one.