Here's an interesting article from the New York Times Science section summarizing some of the research on same-sex and opposite-sex relationships. Here are some of the interesting findings:
(1) “Same sex relationships, whether between men or women, were far more egalitarian than heterosexual ones. . . Partners [in same sex relationships] tended to share the burdens far more equally.”
(2) Same-sex and opposite-sex couples have about the same amount of interpersonal conflict but same-sex couples had a higher degree of relationship satisfaction.
(3) When same-sex partners engage in conflict, they fight more fairly—“making fewer verbal attacks and more of an effort to defuse the confrontation. Controlling and hostile emotional tactics, like belligerence and domineering, were less common among gay couples.”
(4) During a conflict episode, opposite-sex couples were more likely to develop elevated heartbeat and adrenaline surges; after the conflict, opposite sex couples are more likely to remain in an agitated state.
(5) Same-sex partners seem better able to take the perspective of their partner than are opposite-sex couples, perhaps for obvious reasons.
(6) The demand-withdrawal pattern observed in opposite sex couples [“the woman tends to be unhappy and to make demands for change, while the man reacts by withdrawing from the conflict”] seems common in same-sex couples as well. So, it does not appear that this pattern is deeply rooted in gender.