The men's shirts are a bit more offensive because there's societal momentum behind it. Well, "worse" may not be the best way to put it. More harmful, let's say. I mean, not that many people believe that a man's place is serving women. But plenty of people (male and female) believe that women should serve men. The men's shirts are more harmful because there are far more people who take the worldview behind them seriously. It's the same reason that white racism is taken more seriously than black racism. Are they both bad? Sure. Stupid and small-sighted, no matter who's being racist. But whites still hold a lot more political power than blacks (even with a black president). Whites still have better chances at promotion. Police are less likely to target whites. So, yes, while racism or sexism is wrong no matter who's doing it, there are times when you can say one side is more dangerous than the other.
But yeah, that all being said, both sets of shirts are pretty stupid. Pity, because as folks have said, Spencers has some cool stuff.