When my wife and I were first looking into WLS 20+ years ago, there were several newer procedures, including the MGB mini-bypass, DS duodenal switch and the VSG vertical sleeve gastrectomy, that were circling the periphery of bariatrics, which at the time was mostly lap bands and the RNY gastric bypass. These were the only procedures that were endorsed by the ASBS (American Society of Bariatric Surgeons) - the predecessor name for today's ASMBS. Since that time, the DS, VSG and newer SIPS/SADI/"Loop DS" that have gained endorsement from the ASMBS and general insurance coverage in the US. The MGB never made it past that hurdle here in the US, so isn't commonly done or covered by insurance. Bile reflux seems to be the major legacy problem that caused the profession to move away from it at the time. There are claims that some new techniques have been developed to minimize that problem, and maybe they do, but it's a hard sell to make it mainstream in the US. It has become more accepted in other countries.
Overall, being in the States, I wouldn't be overly eager to go with the MGB as it is not commonly done here, so there are fewer MDs around who are familiar with its' care over the long term; the RNY, in contrast, has been done for around 140 years for reasons other than weight loss, so is a well known configuration in the medical world, as are the problems one may encounter over the years. If you have an unusual configuration like an MGB or BPD/DS, it can be harder to isolate any health problems one may have years down the road owing to the general unfamiliarity with the procedure -at least the DS has significantly better weight loss and diabetes results than the other procedures to make that a worthwhile consideration.
If you live in a country where the MGB is commonly done, then it would be a worthwhile consideration, but the US has too many other mainstream procedures commonly available and accepted that do as well or better than the MGB that it doesn't make much sense here.