Always been Oasis Class, they just have so much to offer. I will say though that I've done them quite a few times and it's gotten a little stale (particularly Harmony), sometimes it's nice to switch it up and I really enjoyed Quantum Class. Wouldn't say they are my favourite, and Odyssey is definitely better than Anthem, but fundamentally they are still big ships whilst offering something different.
I have done Radiance, Freedom, Vision & Voyager Class before, but all several years ago so not recent experiences. I was only a child when on Vision Class and it didn't suit us at the time, now as an adult, I'd be open to giving them another try. The other 3 classes are what made me fall in love with cruising, so good memories with them.