I think your reasoning is spot on, @Tim. I know that these days the manufacturers do make a point of emphasizing how their products are specially suited for a male OR a female. I remember when these products, such as the Depends of a long time ago, were basically unisex. These days I use either the Prevail daily underwear which is unisex or Alyne underwear in the male style. Both work equally well for me. I wouldn't think there would be a whole lot of difference in the placement of the absorbent pad (except maybe two inches) because when you gotta go, you gotta go! And that could still end up all over the place, whether the pad is more to the front or more to the rear.
I guess it just boils down to cosmetics. I think the female style would have more feminine colors (so who's going to see your underwear anyway?) and the male style has a plainer appearance. And trying some samples is a good suggestion just because it won't hurt to see if you're missing out on something even better than what you're already using!