No, no difference. A couple is a couple no matter what combination of genders they are.
Either way, what kinds of aspects your natal placements make with each other's reflects the dynamics of the relationship. If it's a romantic relationship, the dynamics will manifest one way, while if it's a platonic relationship, they'll manifest another. The same synastry could indicate either a romantic relationship or a platonic one, and could belong to people of opposite sexes or the same sex. There's no way to tell just from the charts. It takes the actual people involved to fill in the details.