kirby

Not sure, they both have damn best the same abilities and characteristic.

Buu- eats everything, kicks ass.
Kirby- eats everything/everyone, kicks ass.

Both pink blobs...

Yep

Kirby has dealt with planet destroyers and even universe destroyers before. For him, Buu is nothing particularly special. Maybe he's up there with some of his toughest opponents, but look at Kirby. Does that look like the face of mercy?