My sister had the gastric bypass a little over a year ago and has lost a lot of weight. She opted for bypass vs. lapband because her doctor told her that the band can sometimes slip.
Also, be aware, she was told (by someone at the hospital) that insurance would cover the plastic surgery she would need afterwards. She found out later that that was not true.
As for the skin readjusting, as we get older, our skin elasticity diminishes and is not as able to shrink as when we're younger.
The upside is her diabetes basically went away along with the high blood pressure. Unfortunately, the pain in her joints did not go away; she's been diagnosed with arthritis in her back, something we share.
Best of luck on whatever you decide!