Oasis was our first cruise- a big family trip of 15 I think there was- DHs siblings, their families and his parents. We were skeptical about cruising- we LOVED our trip! We loved all the activities in the ship, we had excellent service and food in the MDR, excellent room attendant, enjoyed drink package, Labadee, parade, DD loved the club, the water show, ice show commedien, and hairspray were all great- the ship was so big that it didn't feel crowded, and DD loved all the pools. We will absolutely sail Oasis class again.
We also loved the Fantasy, for other reasons- it was super clean, we loved Palo brunch, CC, Fish Extenders, shows, Mixology, officer pin trading, a lovely magic moment actually to me (I was sent a lovely bottle of wine from an officer I got to know) however we did miss the pools, our dining room service wasn't great, we found the food just ok, I think maybe we were over-hyped, but to us, it wasn't worth double the cost of Oasis (which it basically was, even though we got an good off season VGT rate) we may cruise Disney again, but the Canadian dollar has to recover more and would have to be a GT rate again too.
DH and I also did Freedom (unplanned, totally last minute booking as we were suppose to go to Big Island of Hawaii but our flight was cancelled due to hurricanes and we rebooked our aeroplan flights to Orlando and booked the cruise 2 days before) and had a really nice time also