I've yet to do the rainforest room but from what I've read the dream class ships rainforest rooms are far superior.
We recently were on the Wonder after 1 Dream and 2 Fantasy cruises. She is a pretty ship in beautiful condition but I greatly prefer the Dream class. One thing that really stood out to me and it is very minor, is the hallway walls on the cabin decks. The walls on the Wonder are plain white with a "wood" boarder around the cabin doors, opposed to the Dream class ships that the walls are in the halls being "wood." The halls just seemed more cold and sterile instead of warm and inviting.
As far as getting to places quicker and maneuvering around, the Dream class are only a couple hundred feet longer with a couple extra decks. No matter what ship you're on, if you're an able bodied person, it takes 5-10 minutes to get from top to bottom - front to back.
I also prefer the pool deck layout on the Dream class ships and love Satellite Falls. I'm a huge fan of water slides so the AquaDuck plays a huge role in my enjoyment of the ship.
There are those that claim service is better on the classics but that is really hit or miss. Our best servers were on the Dream, worst were on the Wonder. But our best , by far, cabin steward was Noreen on the Wonder.
If I was in your shoes and wanted to book a second cruise and make sure DH was happy, so you could book a third cruise, I would absolutely be looking at a 7 night on the Fantasy. This is just based on what you said about his favorite things.