I agree with the others saying that you're the one who can make the best decision. We have different situations, cases, preferences, etc., so it would be best to consult your surgeon first as to which is the best for you. Ask everything you need and want to know so that you can weigh things out. Here's a brief comparison I found between the two:
Gastric Bypass
-time tested
-operation is complex, it involves multiple areas of the abdomen
-Rapid weight loss over 3-6 months, settling at final weight 10-16 months after surgery
-Mineral absorption deficiency, requires long-term supplements
-Dumping syndrome (intolerance to sugars and some carbohydrates)
-Not reversible
-No significant hardware in body
Lap band
-a new technology
-Simpler operation, gives lower risk around surgery (less chance of death or prolonged hospitalization)
-Slow and steady weight loss, settling at final weight around 2 years after surgery
-Possible deficiencies due to decreased intake, long-term supplements also recommended
-No Dumping syndrome
-Sort of reversible
-Long term (non-reactive) plastic material in body
-lap band must be adjusted for best success
I really hope it can help you or anyone else..

Best of Luck!