Hi and welcome!
Your surgeon is recommending an operation that he knows how to do, and which is quicker and easier than either gastric bypass or DS. Great for him, not necessarily the best choice for you. If you haven't even heard of the DS, that is a failure on the surgeon's part to provide informed consent, part of which is informing you of all your standard of care options.
With your bmi of 50, the DS may well be your best choice. There is a ton of good info about it on this website, so I would recommend reading everything you can about ALL your options and then making the best informed choice for yourself. The DS has the best statistics of any bariatric surgery not just for percentage excess weight loss, but also for maintenance of that weight loss. Weight regain is a major problem with both gastric bypass and sleeve. The DS also allows for the most varied post-op diet, because we can eat all forms of protein, not just lean protein.
OTOH, with the DS we do need to take more vitamins and minerals, and emphasize protein very strongly. It's crucial, but not difficult once you get into the swing of it. To me, this is a small price to pay for having a much easier time of maintenance. But you must make your own decision. One thing you might consider, though, is that we see more and more people revising from sleeve, lap band, and even gastric bypass to the DS a few years down the line, and I believe (can't prove) that there would be even more of them if they knew it was possible and if their insurance would pay for it.