How a Customer chooses an ATS

If every ATS vendor builds an Applicant Tracking System that looks the same, costs the same and does pretty much the same; how do you choose?

Of course they don't all look or do exactly the same but, in the eyes of an inexperienced Buyer they all feel the same.  But what happens when half a dozen all build their ATS on the Salesforce platform?  What then?  How does the customer choose?

It may seem like a pointless question right now but maybe it isn't.  Maybe if technology vendors could look at themselves from the Customer view point they may think differently.  I see shortlists of ATS vendors that make absolutely no sense to me whatsoever (like comparing a burger with fillet steak) yet the Customer must have a reason for their choice.  So on the basis that this already happens, maybe the customer is buying something else; technology is just what they get and NOT what they buy!

So what are you selling?