Tom,
It depends on you, and what you want. IICRC course is all theory and no practical, very good all the same, but a bit heavy for a newbie (I should know)
I have done Prochem, IICRC at Alltec, and NCCA. All are good in their different ways, but IMO, I would say that for someone new, the two day course at Prochem is a good start and gives a good overall balance, with practical demonstration and theory.
An advantage with the NCCA is that it touches on Upholstery as well, although not in any great depth.
Paul Pearce generally does the NCCA and IICRC training and Pete Hargreaves does Prochem. Both are very good instructors.
Bear in mind that all (apart from NCCA) will have products to push, you just have to listen, and form your own opinion as to what to buy.
Good luck