I would not put any stock in what folks over at Cruise Critic are saying. I am a member over there and read quite a bit but am sort of afraid to post anything....they are negative for the most part and quite snarky the rest of the time. Especially if you disagree with their thoughts on the most inane matters you can think of.
That being said, the information on this board is usually more helpful.
We have sailed the Dream 2x (soon to be 3rd for my DH's 50th birthday) and the Fantasy 5 times. We prefer the 7 night cruises, because by the time we unpack and settle in there are still 6 days left to have fun and relax.

On a 4 night cruise, it seems like we are constantly packing and unpacking.
I have 13 and 14 year olds who insist that they prefer the Disney ships far more. They spend some time in the clubs, but for the most part, just kind of relax and do their own thing. I am trying to convince them to try RCL and NCL but so far no luck. And my soon to be 50 year old does not want to sail any line other than Disney...so....there you have it.
You will love the Disney cruising experience!