Frankly, it'd be his decision, one way or another. To be honest, the boy is darker than he ever will admit, in any incarnation. Frankly, the one that's been here longest only ever stayed in the light out of stubborn refusal to give into those darker urges that he very frequently has. I think it has to do with the whole split soul thinger that most of them don't have. But you didn't hear that from me.
He's a dark soul, like his father. It's not a flaw. And the more he struggles against it, the harder life in general will be for him. I'm not saying he's evil by any means. No Skwigelf has been evil. Simply... dark.