The doctors at Primary's told us that they do not currently have a "senior" surgeon since he had retired not too long ago due to him getting pancreatic cancer. All of the other surgeons were considered "junior" surgeons.
They said they could do the surgery, but felt more confident in sending us to a surgeon that had more experience and confidence. The main thing that the junior surgeons would not be completely confident about was the subvalvular stenosis. Everything else they would be good with.
So from my knowledge, the main reason we are going to a different hospital other than Primary's is because of the subvalvular stenosis.
(I also found out afterward that the other hospital could do everything in one surgery and not have to stage the surgery into 1 or 2 different ones. yay!)