@Amy does both methods help with stabilising the endometrial line?
Yes, they can help.
It depends on the type. There’s full hormones pill or progesterone only, there’s the copper non hormonal iud or mirena etc. Also each type unfortunately affects every woman differently so it’s impossible to say how you’ll react without trying them.
Both would be protective for the endometrial lining. The hormonal IUD is great if you have trouble remembering to take pills every day, whereas the pill can have additional benefits (depending on which pill) if you struggle with acne and facial hair growth associated with PCOS. You may not get a period with the IUD, but that is because the endometrial lining is kept thin (different then when you skip a period and the lining thickens when you're not on contraception). I've used and loved both - personally, the IUD was my favorite because I didn't have to worry about taking it every day but I had better skin on the pill. The non-hormonal IUD won't help with menstrual regularity or PCOS, but is good birth control (if you wanted to just continue the provera as needed).
Oh I change my answer to B now after reading the entire question
When I had my IUD, I never had a period. Took a few months to regulate, but after that, I didn't have a period for 7 years. If you're trying to have a period, I wouldn't suggest an IUD. I'd do pills then.