ASME uses AIs, better known as Authorized Inspectors. Most of them have engineering degrees with several years experience in design and fabrication or several years of experience operating boilers and related equipment. My instinct tells me that it would be a reach for the average welder to grasp all the information and background required to pass the requisite examinations.

API would be within the grasp of the average welder as would the CWI. The candidate for each would have to determine which industrial sector he wants to work in, oil patch or structural. That isn't to say there aren’t similar requirements for each, but in general the API certs are required for working in tank farms and refineries where as the CWI cert is needed to work in structural steel fabrication shops which could include bridges, buildings, rolling stock for railroads, aerospace, etc. From that aspect, I believe the CWI has wider applicability and is accepted by more industries that either the AI or API certifications.

I maybe biased in my views, but "I call em the way I see em."

Best regards - Al