I actually don't have a medical background, just to be clear, but I'll see if I can answer your question. I think what Dr. Gmora is getting at, is that the VSG is not reversible - they remove most of your stomach and throw it away and there is no way to get it back or reconstruct it. Whereas with the RNY there is nothing removed and it can be reversed - though this is a very major surgery and almost never done and can have serious complications itself.
I've looked at studies that compare the risks for RNY and VSG and they have about equal rates of surgical complication, just different complications. I would ask Dr. Gmora to show you studies or some statistical information to support what he's claiming. Something *could* go terribly wrong with any surgery. The updated position statement from the American Society for Metabolic and Bariatric Surgery says that meta-analysis of existing VSG studies found serious complications (including bleeding, stricture and leaks) to be about 4%, compared to RNY at about 7% (if you consider an ulcer to be a serious complication, the rate for RNY doubles, whereas this is very rare with VSG). Dr. Gmora may be of the opinion that while serious compliations for VSG are more rare, they are harder to treat, which I can't really comment on. But if you look at the mortality statistics, the numbers for VSG are even better than for RNY, so people are obviously generally surviving even the serious complications.
If you still think the VSG is right for you - ask for a second opinion. Dr. Anvari or Dr. Hong can have a look at your case and make a recommendation as well. In the end it is you who has to live with the surgery for the rest of your life, not the surgeon.