Long Arc
Lawrence answered your question.
Logan started saying something about API 1140 being easier, and how if you got into the structural your future boss might want you to obtain the D1.x before you were hired.
Actually The AWS CWI exam is a test that certifies you as a CWI. You can test in numerous codes for the open book part of the exam API, D1.1, D1.5, D1.2, D15.1,....
When you pass the test you qualify to perform the act of weld inspector to all the codes. I am not an AWS CWI D1.1 even tho that is the code Test I passed.
I showed by my ability to interpret a code test, my ability to do just that interpret code.
So when called upon to inspect a weld the only thing I need is the Code books governing that situation and I am qualified to interpret.
I don't know about the API code being easier, it and other of the code books are definitely thinner. I contemplated going that route in my application process but the fact that my background had mainly been Structural since the early late 70's to early 80's when the Oil fields dried up, I opted for the D1.1. I passed the test 2001.
So as you investigate this step you are contemplating in your future, Rely on your past to guide you.
http://files.aws.org/certification/CWI/CWI_Exam_only_pkg.pdfHope this helps more than hurts.
Marshall