I know I already answered your other post and mentioned I'd take the Dream over the Wonder but I don't have anything against the Wonder - just prefer the Dream.
There are some that feel like I do - which feels to be against the grain - that feels the Wonder and Magic are MORE crowded. My DH and DS had only been on the Wonder as a classic ship, but had already sailed twice on the Dream. We went on the Magic in January (and loved her) and then last month on the Fantasy. They had not been on the Dream since 2012 so I couldn't wait to hear what they had to say last month on the Fantasy. They immediately felt there was more room, it wasn't as crowded, etc. I don't want to put down the Magic or the Wonder because I seriously would sail tomorrow on them if I could.
For example - the elevators on the Wonder/Magic feel so tiny compared to the Dream/Fantasy. We honestly could barely take the elevators on the Magic because they don't hold as many people and every time the door opened, it was jammed back. Not a biggie but this happened over and over. The Spring Break on the Fantasy was sold out and we didn't have this issue - again the elevators are bigger and you can squeeze more people.
We also much prefer the layout of Cabanas compared to the Wonder's Beach Blanket buffet. Cabanas can be nutty, but you aren't required to stand in line, one line and wait your turn and the options are so much better on the Dream/Fantasy.
The kids club is a big difference as well on the Wonder vs. Dream - much more improved on the Dream since she is obviously newer. The Magic (I know you aren't deciding on the Magic - has an AMAZING kids club after the re-imagining). My DS definitely liked the Lab on the Dream/Fantasy over the Wonder.
I'm going on the Dream for the 5th time this September with my Mom and I feel the Dream also has an amazing crew - heck, they all do! I've sailed all the ships, some repeats and I don't typically like to put one "down" but since you asked, I felt the need to be honest and stick up for the Dream - lol
I think you'll need to pick one now, then choose the other later and see how you feel. They will all become special to you for different reasons! The Wonder to Alaska was our favorite cruise so far but my favorites ships are the Fantasy and the Dream.
Heather