I previously was on a much smaller ship (Rhapsody of the Seas) and wanted to see the difference. While I do like the smaller size of Rhapsody for getting around easily and less people, I admit that I much prefer Oasis for it's entertainment. Every night we went to a different show and each was very professional. There was an ice skating show, high diving & synchronized swimming show as well as comedians, jazz and bands every night. The food was good in both the MDR and buffet. I'm not a foodie so I couldn't see paying for a specialty restaurant for us when the free offerings fit my needs. I did buy the deluxe beverage package and I know I drank more to make sure I got my monies worth. But the bartenders all poured strong and tasty drinks.
I couldn't win at all in the casino which was a bit disappointing. In the Rhapsody I won enough to keep playing but the slots on Oasis were super tight.
The room was pretty big compared to Rhapsody - we had an interior room which looked out onto Central Park (not a balcony). Room steward was great and kept our room clean.
I don't remember the category. It had a picture window that overlooked Central Park. The room was spacious enough for two people.