I think, originally Oasis class was only planned to be used in the Caribbean. Wonder was supposed to go to Asia initially, so she shares some similiarities with Quantum-class ships, like the renaming of Dazzles into Music Hall and the additional casino in place of the Disco. In Oct. 2019, we were on Spectrum of the Seas out of Shanghai to Japan and certainly appreciated the fully enclosed Solarium. As an added perk, on Quantum-class ships doing Asian routes, the Solarium is part of the Suites area, so it was never crowded.
Windjammer is definetly bigger, it was moved down one floor compared to the other Oasis class ships which allowed them to do a circular design, opening up room for additional seating.
However, I'll certainly miss the lounge chairs in the Aqua Theatre, not sure why they got rid of them. My guess would be capacity, on a bench of the same lenght you probably get almost double as many people compared to a row of lounge chairs.
Another thing which is different on Wonder compared to the other Oasis-class ships is the shows. Would have loved to see another musical onboard. But with the initially planned deployment of Wonder in Asia, I think they were trying to put in shows which don't depend too much on dialog.