I think both companies and women would benefit from quotas on corporate boards. It's no secret that there is a glass ceiling that is very difficult for women to break through. The status quo is to prefer white men as board members and I feel a company could bring in a lot of untapped talent and really exhibit that they are on board with equality by hiring more women in higher up positions.
No, companies would not benefit from quotas for women on their boards, because the women that are on the boards would be treated with skepticism. People would not believe that the women on the board really deserved their spot, so what they say would not be given much weight. It is better to give everyone a chance, based on their merits.