The biggest difference is in the number of anastomosis or cut/joints.
The standard gastric bypass surgery (GBS), also known as Roux–en-Y anastomosis, involves two anastomoses with the intestines. This means more time and chance for complications.
Conversely, the mini gastric bypass has the huge advantage that involves only one anastomosis. That’s why this procedure is also known as the one-anastomosis gastric bypass or Omega Loop GB.