Having been on The Vision of the Seas not that long ago, the beds are of the same high standard as the Oasis and newer ships. They are very comfortable and I sleep better than at home in my own bed. The bed grade is about a 3, 1 being so soft your bum hits the floor and 5 being so hard its like a table.
Alot of the things both cruise lines do are the same, but there are little differences between the lines, the choice is yours. I prefer RCCL for the ship and entertainment.