A 35-year-old multiparous woman with a history of dysmenorrhoea and menorrhagia (soaking 6–8 pads per day for 6 days) requests long-acting contraception. She has no contraindications to hormonal methods and wishes to avoid surgical intervention. On examination, she has a normal uterine size and no adnexal masses. Pelvic ultrasound shows no fibroids or adenomyosis. She is counselled about both copper T380A and LNG-IUS. Which device is most appropriate for this patient, and why?