It's interesting how many people prefer the Wonder AND it was the first
DCL ship they sailed on. It could be that the preference is driven by nostalgia.
Our first (and second) DCL cruise was on the Fantasy and we found the Wonder disappointing in comparison. Could be down to nostalgia and better itineraries, however my wife and I really enjoyed the Meridian bar sitting outside having a drink outside at the back of the ship, and the Skyline Bar for the cocktails with an international flavour and the changing cityscapes, and the kids loved the Aquaduck and Midship Detective Agency. We missed those things when sailing on the Wonder.
We also had trouble sleeping on the Wonder as it was really noisy, and I don't mean engine or other passenger noise. We initially thought the nighttime noise was rodents and reported it, but we eventually worked out that it was old fittings rubbing together and against the walls. Not great.
The Fantasy was our first ship and we sailed her several times before the Magic and Wonder, so it isn't nostalgia for me. I love the Fantasy, but I don't think the extra real estate really adds much for me, as it doesn't really seem like it increases the size of many spaces in proportion to the extra people it adds, with the Atrium probably being the biggest exception. I do like the upper deck areas of the adult pool area on the Fantasy more too. I also like the undersea vibe that Animators Pallet has one night, which I miss on the Wonder.
I like to sail aft (particularly now that we are getting ADA rooms for my daughter) and the vibration issue is real on the Fantasy, so we actually found the Wonder to be
much better for sleeping and noise in the room. The last time we sailed the Fantasy, it felt like one of those dirty motel room vibrating beds and the room made a high-frequency rattling noise in all directions much of the time. Even sitting in Animator's Pallet, it was a small annoyance at times.
I very much like the UK and Irish themed bars, plus Keys and the Cadillac Lounge on the Magic and Wonder over the Fantasy bars too. They are places I like to hangout, where as the Skyline is a bit too dark and modern for my tastes, and that Carousel one feels strange and is too open to kids running through. But I do really like Ooh La La and missed it on the Wonder.
We also only go to the one main theater production now, and Aladdin isn't my favorite. The last time I saw it, the production value just wasn't great, and I find it jarring to see someone try to replace Robin William's perfect genie. I thought the same thing would happen with Olaf, since Josh Gad is so good, but the actor was spot on and really captured the original character.
I also like that the Wonder dumps less people in port.
In the end, they are both great ships that I love; I would pick the Wonder first, but would still be thrilled to be on the Fantasy. We are sailing the Celebrity Edge this August, which will be where the real differences pop up. I am beyond excited to see how we like it.