As you can tell by my signature I am biased toward the Magic.
Will list the pros and cons for each
Magic
Pros
1. Smaller ship less people and less congested
2. Staff is much friendlier. Did the third trip on the reimagined magic and all the staff were super friendly and personable. 2 months later on the Fantasy the same staff that had transferred back were much less friendly and personable.
3. Quit Cove pool is bigger and you can swim mini laps, and seems to get more sun
4. Dining rooms are more relaxed and the serving stations are laid out better making the server teams more efficient and in a better mood.
5. Aqua dunk is great and the new splash zone in the little kids pool area seemed to be used more than similar area on the Dream or Fantasy.
6. Fathoms is awesome and for us is a much better venue for shows than the tube.
7. Cruisers are more personable, might be due to the smaller number of people on board, and a bit more relaxed pace than the Dream.
8. Gyro station, at least when we were on in January

9. The pirate show includes the fireworks as part of the show.
Cons
1. Rainforest room is nice, but no where near the Dream class.
2. Not as much technology, like no midship detective could be a downer for some
3. No mini golf
4. No satalite falls
5. No skyline lounge, miss that the most, great place to have a martini and debrief the day.
Dream
Pros
1. Satalite falls when they get it.
2. Technology midship detective and magic portholes
3. Mini golf
4. Rainforest room (we did fantasy and assume dream is similar)
5. Skyline lounge
Cons
1. Bigger ship and the pool decks can get crazy
2. Because of the number of people and 2 pirate shows, fireworks are just fireworks.
3. Dining room experience is not as relaxed.
4. Staff not as personable.
For us it is a slam dunk to go on the Magic, we have a B2B scheduled next year. Our favorite ships in order are the Magic, Fantasy and Wonder a draw and the Dream is our least favorite. Saying all this we have enjoyed all of our trips you really can't go wrong on which ship you pick.