DKCTF, easily.
DKCTF and Astro have the same sense of flow but DKCTF does it way better (granted, it's easier for a 2D game, but i'm still making the comparison because it's the choice of Astro to be constrained and thought out in this way) with a better sense of challenge. It's also a game that revolves around the companions ability as a plus but the core gameplay is really about the moveset of Donkey, and the hard mode show how well designed it is. In comparison Astro is prescribed, and revolves around a variety of fresh little mechanic.
Astro, like most Sony games, is really almost a sensory game. Put the comfort and the feeling of the player above anything else. And it's obviously also a blockbuster for the platforming genre.
But DKCTF is better designed, and has imo a better atmosphere/personality, with a killer OST.