I want to preface my comments by saying that until we took an Oceania cruise to the Baltics a few years ago I was through with cruising. I had been on four lines (one a small South American one which I loved) and I just wasn't fond of cruising. It might have been the ports and the Caribbean. But friends convinced us to go with them to the Baltics on Oceania, which we knew had a very good reputation. It was wonderful. WE had never been to the Mediterranean and were planing to do a land/sea tour when we found a great itinerary from Oceania so we decided to try ti again.
The new Riviera was a bit daunting to us after that small boat from Oceania, , but we loved it. What do we love about Oceania after two cruises? The no-dress-up policy, the very high quality and variety of food, the terrific people we met on both cruises, our more spacious veranda room on the Riviera, the variety of activities on the boat and the various places you can go when you are at sea, the terrific staff and personal attention, etc. I also find it pretty hassle free, although we were not happy with the restaurant reservation policy for both our one-night bookings and when trying to get return visits to restaurants (which many people were more successful at than us).
Larger veranda room than on smaller boats. Much better bathroom with two showers. We had trouble with our veranda door the first day. ad they came right away to fix it., We received almost a call a day to make sure it was fixed and working properly. That's what we call service.
Overall the choice of ports is superb and we loved the extra night stays in ports. Occasionally there are itinerary changes and changes in docking time and that does not make me happy. But given the cruise lines out there, I would go Oceania any day.