I know you didn't ask me this, but I've been hanging out on BP for several years. A lot of people (although I obviously can't speak for alissajs specifically) choose the sleeve because they feel it's less invasive than the bypass. Although I think they both could be considered pretty invasive - cutting out 80% of your stomach and throwing it in the trash seems pretty radical, too - at least to me...
I think a lot of people also know about horror stories from 30+ years ago, when they used to do severe intestinal bypasses. The RNY is actually a gastric (stomach) bypass, so it's not the same "bypass" surgery they did years ago. They DO bypass part of your small intestine in an RNY - but we're talking about maybe a foot (to do the "Y"). Years ago, with those old intestinal bypass surgeries, they used to bypass many feet of small intestine (and the stomach wasn't bypassed at all - so very different surgery). No one does those anymore....haven't in a really long time. Anyway, a lot of people who had those ancient surgeries got very sick from malnutrition - and some died - and I think some people are remembering those and think that's what they're doing now with the RNY. But they're not..
