>>110137379I'm going to say Keroro is more incompetent, since most of the competence is distributed among his teammates. Even then, their competence is limited by personal flaws.
Zim's a one man show. He is incompetent, but also a savant idiot. His 'teammates' are incompetent too, so out of them, he's the one carrying the most semblance of a braincell.
In a knock down, drag out fight, no keroball/pak gadgets and no help, I'm not sure who would win.
Though upon discovering each other, the reaction would be a similar "Ughh, an Irken/Keronians."