Hi Leslie and C-mar and welcome to you both.
Both centers noted are highly reputable in effective radio treatments of AN's. There are many radio protocols (ie: GK, CK, FSR, Trilogy, etc) that are very effective in the treatment of AN's. Suggestion is to take a peek at our "Radiation/Radiosurgery" section of these forums. There has been, over the years, vast discussions of efficacy of each versions, technologies used, etc.
In our "Post-Treatment" section, you will also see many, including myself, noting our post-radiation outcomes.... some good, some not. It truly is a situation of "individual results may vary" and we don't sugar coat things here. There is no "idiot proof" version of radiation for any AN's (CK is LINAC robotic and image guided and yet, like all radio options, I personally know good outcomes and some not so good) but experience of the treatment teams is essential when chosing a treatment option (regardless if surgical or radiation).
What I can share is that your "gut" will help guide you to what is best for you and your particular, unique situation. Each AN is unique to itself (ie: location and size of tumor, your locale, insurance coverage, etc). Best suggestion is doing your homework fully, taking use of info, such as these forums and info that the ANA office can share (including the home website) and most of all, patient referrals.
Rocky Mountain and Pitt are wonderful options (if you research the historical here on the forums). Either way, you will know what is best for you.
Hope that helps... and again, welcome to you both!
Phyl