what's the difference?

So the big reason as to why is because Gamecube is faster than PS2.

An important thing to note, however; is that in Dad's Dream the Gamecube version has a chance to crash at every instance you use the Klaxon. The PS2 version does not have this problem.

Load Times on the PS2 are much slower than the gamecube version. The gamecube generally has faster load times for most games.