It's all relative. Women in general aren't as physically suited to that sort of endurance as men, or at least not without the quality suffering. It would be torture watching the likes of Schiavone and Safina play four or five hours of increasingly low-quality tennis just because it was seen to the appropriate that they play the same number of sets.
There's also the fiscal argument as they don't generate even half of what the men's tour does in terms of revenue. But then you have to go down the road of giving less prize money to the less popular male players as they won't have generated the same amount as the likes of a Federer or a Nadal.
This is achieved by the inherent meritocracy - the biggest tournaments pay the most.
I think if women want equal pay at Wimbledon, then they should play the same number of sets. Fair and simple.
Also, I hate how the final can be over in two sets - makes it a huge anti-climax.