>>73181 (OP)
Assuming both couples are in average physical fitness and there's no athletes or martial artists, a man will typically win in a fight against a woman due to a higher natural strength. A straight couple is always 1 man 1 woman, but a gay couple is either 2 man or 2 woman. Since it's equal numbers the fight is going to come down to who has the most men, which means the gay couple wins 50% of the time in theory.
In practice however, there's a slightly higher chance fur the gay couple to be female, about 53%. Which means that the total winrate fur straight couples would be about 53% while gay couples would have a 47% winrate.