Wow, this is a great thread. I'm 5 days out of surgery, so I can't really say I have a ton of experience with the DS yet. But, I did think about this choice, so I can add to that.
I think most of of the people have covered the core reasons - it works over the long run, it lets you eat food again, you don't have to struggle anymore, dumping scared me, etc. And Diabetes was a key issue for me, so that was another check box.
But, to add another perspective to the thread, it was clear to me that people with the DS were much, much more happy. I did a fast, like optifast and took off 120 pounds about 10 years ago. I loved the guy who ran the program. He has been in this field forever and stay in touch. When I started to really research surgery, I went to him. He knows 100's of people who have done every type of surgery and he said, the only group people who are happy (and also by the way, thin) are the DS people.