Although we haven't sailed on Oceania for some time, we've always consider the food on Oceania the best at sea. Silversea's food is fine, but there were many more memorable dishes on our Oceania cruises. Although the food on the Silver Galapagos was right up there with Oceania quality -- except for the non-local beef, which was pre-cooked and frozen on the mainland.
Seabourn's food is acceptable, but nothing really stood out except for one or two Keller meals we had. Our biggest complaint with Seabourn is the overcooked fish, especially the halibut. Even when we ordered it rare, it came out like cardboard.