I have been a CVSA examiner for a few years now and by no means, am here to sell you the machine.  What I will convey is the truth from my position.  I have taken many truth verifications over the years, to include CVSA's and polygraphs, and can say, without a doubt, neither are always going to be 100%.  After gaining my certification as an examiner, I began understand why neither test are admissible in court; simply put, the machines are only as good as the examiners.  If you have a poor examiner, you will have a poor result from the machine.  If you have a good examiner, favorable results can be expected from the machines; this is not specific to one machine or the other; they both are in line on that metric.  Having said that, the CVSA has been an invaluable tool for gaining admissions, information, and truthful statements.  The CVSA a tool, nothing more.  The polygraph is a tool, nothing more.  Those who argue over the accuracy of one vs another are simply arguing their confirmation bias (i.e. a polygraph examiner will tout the poly and a cvsa examiner will tout the cvsa).  If you wish to take an objective approach here, then you must see past the subjective opinions being offered and ask yourself this one question:  if both are just tools on an equal playing field, why are we limiting ourselves to just one?