You are correct JW.
I guess my point is that every machine is the best and the worst at something.
If the Cyberknife was a ferrari, Novalis TX a Rolls Royce and Gamma Knife the Toyota Prius.
All 3 of them can take you from A to B up the freeway, and if you drive at the speed limit the end result will be the same.
If you have a need to get their quickly you would use the Ferrari.
If you need to get there in utmost comfort for an elderly millionaire you would take the Rolls Royce
If you need to use as little fuel as possible you take the Prius
The same problems arise in Radiosurgery. Each machine was designed to be good at something, but it can never be great at everything.
What you should not do is attempt to travel in a model T Ford on a 100 degree day at 65mph, with somebody who just got their license.. That is bound to be trouble.
I guess my point is that if you could give a medical team any machine they wanted to perform Radiosurgery, they will probably use all 3.
Each machine has its advantages and disadvantages depending on the size, shape, and the location of the tumour.
Novalis TX is a Varian Linear Accelerator fitted with a Brainlab Multileaf Collimator
I found this research paper comparing BrainLab and Cyberknife for Acoustic Neuromas
It should be noted that the tumours in this study were quite small, which would favour Cyberknife.
Larger odd shaped tumours, may have given a totally different result. http://www.researchgate.net/publication/51619115_Dosimetric_comparison_of_Linac-based_(BrainLAB)_and_robotic_radiosurgery_(CyberKnife_)_stereotactic_system_plans_for_acoustic_schwannoma/file/d912f4fa035f9af4d4.pdf?ev=pub_ext_doc_dl&docViewer=true
It should be noted that the latest machines, with the best operators, are producing very similar results for AN's
So while in theory one machine maybe better than the other, its not really showing up in the published results so far.
It could be that the latest versions of all machines in the hands of the best teams, the differences are becoming more academic and theoretical than practical.