Dan, IMHO. I really don't like either one. (Sorry, I know Mayson is actually pretty well liked, but I really don't like her.) And despite my twin, I can't stand Dan either. But my reasoning for saying Dan was more in the way... Mayson was never really a roadblock except when Lois was already pushing Clark away. Dan, OTOH, was constantly in the way. Mayson never would have been in between them if Lois hadn't allowed it.
Jana