With OB you can pay per module ($110) and you just download them as you go. Or you pay for all 4 at once and get a discount. OB does not supply hardcopy manuals it's all electronic.

with CBI you can pay in installments and get electronic access to all of the materials on line in the student area of their website. Once you pay the final instalment they post you all the hardcopy manuals (there are three). If you pay upfront (which I did) you get the same access to the website and they send you all of the hardcopy manuals when you start.

I have to say I really liked the CBI manuals and I still refer to them now.