Oral contraceptives offer a regulated, low-dose combination of estrogen and progesterone to prevent ovulation. Because ovulation is difficult for many women with endometriosis, this can be a big plus for OCs. Also, women who stay on the pill often have reduced menstrual flows and fewer cramps. Mild disease can remain quite stable for long periods of time. Side effects are relatively minimal for most women, and expense is not great.
Progesterone can also prevent ovulation and reduce circulating estrogen levels.
Side effects include irregular bleeding, bloating, weight gain, and more. Expense is reasonable. In my opinion, depo provera is not a good choice for women who have not completed their childbearing. A certain percentage of women who take depo-provera never ovulate again. The results are very similar to menopause, with some differences in the FSH and LH levels.