All a matter of opinion. Personally, I felt the ICC's were easier. And, while they do have a portion devoted to plan reading, it isn't that bad either as long as you have at least some background in multi-story building plans. Being familiar with plan schedules, typicals, notes, details and how to bounce back and forth between several all to answer one question.
Of course, you will need original copies of the IBC preferably 2012, AISC Construction Manual which will have the RCSC code on bolting; but I'm getting ahead of myself. All you have to do is go to the ICC website and it will direct you to the resources to use on the exam and everything that is needed to apply and prepare.
The welding portion is easy since you have your CWI. After you pass the Bolting portion ICC uses what they call a 'transition' form that is basically a cert by reciprocity. All it takes is more money.
Unless of course they want you to actually take the exam. All depends upon what the company, or a customer, wants.
He Is In Control, Have a Great Day, Brent