This is hard to judge since gaming feats get weird with franchises as populated with games as Kirby. For example, in Milky Way Wishes, Copy abilities are basically collectible permanent power-ups, Kirby can freely swap between any copy ability he has without the need for inhaling anything (you can't actually get abilities via sucking there iirc). If we consider that Kirby for example, it's a different conversation from regular Kirby, especially with the Copy ability that would allow him to take Goku's ability.
That said, I just think Kirby would be able to absorb Goku anyway. The reason Kirby can't absorb bosses tend to be that the massively out-scale him in size, Goku's size at most would put him at mid-boss level, where he'd be able to absorb him after beating him (which isn't useful in the fight but still). But Smash Bros. shows that he's capable of absorbing people Goku's size (and he can't absorb bosses in those games either).
And while Smash isn't mainline Kirby game, but Sakurai is the creator of both. I don't see why I wouldn't trust the creator of Kirby to know Kirby's capabilities, so I think Smash feats are valid, especially with the story modes Sakurai penned for them.
Regardless, I suppose I can see either winning but I'd probably lean towards Kirby. Might just be bias though.