Masculine words have prevalence when generalizing. This is true, for example, for professions. "Врач" (masculine) is both male and female, while "врачиха" (feminine) is vulgarism.
So "поженились" is correct.
"Выйти замуж" is also correct, but has stronger meaning of a "role" in a pair, which may be not adequate if partners are "universal".
Any term is expressing role, but "поженились" does this lesser, so it is more correct.
Examples:
Оля женилась на Кате (slightly expressing Olya is active).
Оля жената (clear that she is lesbian).
Вася женился на Пете (slightly expressing Vasya is active).
Вася женат (not evident if homosexual or not).
Они поженились -- correct for men.
Они женаты -- correct for men.
Вася вышел замуж за Колю (strong expressing Kolya is active)
Вася вышел замуж (clear that he is gay and expressing is passive).