Hello dear, thanks for your question!!
Both procedures are excellent for weight loss. Sleeve gastrectomy is restrictive procedure- it works by making your stomach smaller so you will not be hungry with a small meal. Gastric bypass adds a reconfiguration of your intestinal tract producing malabsorption. Weight loss out to eight years is the same for both procedures. Sleeve is less risky and has more rapid recovery- most vitamin absorption is normal. Bypass involves more work, has longer recovery and you must be committed to vitamin supplementation for the rest of your life.
Both operations are great effective operations performed in the hands of an experienced surgeon. In making a determination on what is a suitable operation for an individual multiple factors need to be considered. Nutritional factors such as underlying vitamin deficiencies, your eating habits and hunger level.
Good luck :)