Magnesium Vs baby asprin

Does anyone have any advice on which would be better to help keep elevated BP down during the third trimester? I’m currently a little over 33 weeks and I’ve struggled with slightly elevated BP since the beginning and my OB told me it would be better to take baby aspirin rather than the magnesium. I haven’t started either one yet, but I was always told baby aspirin wouldn’t help with me being so far along already and it’s best to start it when I first found out I was pregnant. Has anyone used magnesium to help??