Hi Ed,
I took a look at the website on the Perfexion - nice videos! Besides various nice-to-have features, it has a more flexible beam positioning system, which is computer controlled. This would allow them more flexibility in the treatment plan, because they can move the beams a little without moving you. In theory, that would mean even less chance of hitting the hearing nerve, or whatever else they are trying to miss. I don't know of any data that would indicate how much difference it makes for AN treatment.
One of the reasons they developed it, and a hospital might acquire it, is that the flexibility means it can treat more kinds of tumors, in more locations. It is also faster, apparently, so they can do more patients per day. I don't know if any of that makes the treatment of your AN any better though. My guess is that it is probably not much of a difference. The standard GK machine is pretty well dialed in for AN treatments.
Steve