I saw We Love Katamari Reroll + Royal Reverie was on sale (and still is) as a digital download for $10. Can't beat that, so I bought it.
The movement in Reroll is so much more satisfying that it's shocking. I'm still having fun with Once Upon a Katamari, but I would be dishonest if I said it controlled as well. (The gameplay is often much more frustrating.) Even the hitboxes seem less forgiving. Which is bizarre... you would expect them to use the same underlying architecture.
And it really is true that the series was superior under Keita Takahashi's direction. As far as I can tell, he wrote all of the King's dialogue and the item descriptions, and it's all that much more amusing and charming. The King feels like a coherent (if completely absurd) character, and that character comes through in every line from him. I had forgotten how ridiculous and darkly funny those cutscenes are.
However, dedicating a button to the dash move was an excellent idea that OUaK implemented (or maybe an earlier game did that, I don't know), and it's hard to go back to the regular input.
The Royal Reverie levels are... fine? I really wish Takahashi had written the words around them. The idea of watching the Prince's monsterous grandfather interacting with a young KoaC sounds like fun... but of course, there's barely anything there, and the levels are just rearranged levels from the main game. There's not even any new music. A missed opportunity, but at least it's new content.
I probably won't get the original game's Reroll. I don't think it has any new content. But I feel like buying it and pushing it on family. What a great series.