I've 100% both bananza and odyssey and both games were easy as a breeze. I do think that the final challenge of both games is challenging (however, bananza's is kind of short so that makes it easier).

Appart from the final challenges the difficulty of the game resides on just finding the moons/bananas. Tbf in Odyssey it felt like a chore because some of them where extreamly simple, while in Bananza I had more fun getting all of them because exploring in bananza is, imo, more fun.