One other argument in favour of equal prize money is that perhaps the money you pump into the women's game, the more investment there will be, the more youngsters will be able to pick up the sport and take it seriously, and perhaps in the longer term the higher the quality of new players in future.
It's not a perfectly convincing argument but I thought I should suggest it. At any rate prize money is based on an assessment of the funds available, the prestige of the competition and the organisers' view of what's bringing spectators to the game. It should have nothing to do with hours worked. By that argument the prize money in the men's game should also be based on hours spent on the court, so that, say, a gruelling five-set win should lead to more money than a crushing victory in straights. That doesn't happen (although maybe it should!), which invalidates the "but women spend less time on court!" argument.
Quality-wise, I agree that at the moment men's tennis is more enthralling, though.