To quote my answer from another board:
The past few years we've been on Oasis and Vision class ships. Rhapsody, Allure, Harmony. And the Wonder in two weeks.
So really both sides of the ships sizes. And I really couldn't tell which one I like more.
I really love the entertainment on the Oasis Class. Great musicals, good live music at Boleros. Rock climbing, FlowRider, Zipline, the Abyss, Aqua Theater, Ice Skating shows. And lots of specialty restaurants. And then two of my favourite spots: Central Park and the Solarium. It never gets boring. You never end up hungry.
But sometimes it gets crowded (not last time though...running at just 25% capacity). Places like the Solarium fill up quickly. And if you're not fast enough, some specialty restaurants will sell out.
The Vision class is a lot smaller. But I had fun just the same. The Solarium is small, but cosy. A small version of the Park Cafe serves some decent snacks there.
Enjoyed the Schooner Bar on the Vision class a lot more than on the Oasis Class. Felt more intimate...the whole ship does. You keep seeing the same visitors, the same staff. And when everything stops you will keep meeting the same folks grabbing one last slice of pizza before calling it a night. I really liked that.
And there is a charm to the Centrum. Old-School cruising charm with for example the 70s show happening there. Or just to hang out for a late night drink - or pre-dinner drink. Nice dancing nights at the Viking Lounge with great views - missing that on the Oasis Class.
And - at least the Rhapsody - still has our two favourite specialty restaurants: Izumi and Chops.
Really really enjoy both of them. And I would say equally. The cabins are quite bigger and more comfy on the Oasis Class though.