Pierre is definitely the comic relief character of the two. His saving grace is that he is an absolute beast of a character if you obtain his complete Hero Set of equipment, but that requires at least a second playthrough as two pieces are only available in different scenarios based on whether you saved Kid or not. Nikki is a good choice if you plan on doing the Marbule Quest, since his relationship with Fargo and that whole quest plays a large part of his story. It's a shame the most story-centric of the three is also the crappiest character...