I cannot imagine me having either. But if I really had to, I would go with the band. The by-pass is a very drastic procedure and will affect what you can eat, drink, and even what meds you will be able to take for the rest of your life. The band is more forgiving and can actually be removed if necessary down the road. I have an aunt who had the band and it was a good thing. She actually lost weight too fast and they had to relax it.