If you read the long term studies by O'Brien weight loss is virtually the same when comparing bypass vs band. But, the band is minor surgery, totally reversible and carries few if any complications. Furthermore, if you look at weight loss for bypass vs band charted out on a line graph you'll see a slight weight gain for bypass pts in the long term...kind of like a rebound. You don't see this same curve for band patients b/c in bypass the pouch can stretch with the band it can continue to be adjusted.
For me its a no brainer. My surgeon has ceased bypass altogether considering it somewhat barbaric considering the strong results of the band.