I've taken both. Marinol did nothing for me. I think it sometimes helped me not feel full, but didn't entice me to eat at all. Megace was a life saver to me because it worked so well. I'm not on it all the time though - just took it for a few months to put some weight on and went off. I could probably use another round since I've slowly lost most of that weight again -- but I'm nervous about the blood sugar effect too, since now I'm a bit diabetic...