qBank was the first question bank they made. It's got several thousand questions which will prepare you well for Step 1. the IVBank is supposed to be "integrated vingettes", but it has many many of the same questions as qBank. It's formatted such that it has a vingette and then 3-10 questions referring to it.
I had access to both because a couple friends shared a 6 month subscription early on (and then when it came crunch time we got our own since it can only be used from one computer at a time), but I'd say that IV bank is not worth it because of the overlap and the format. Stick with qBank.
I think qReview are like classes -- I want to say they're on the internet? I didn't use them.
I agree, IV qbank is a waste of time. Even a few questions in Qbank tend to be a little bit limited in their understanding of concepts sometimes, as if the question writers didn't have much real expertise in the subject. But I do like Qbank for review purposes.
stick with the one or three month deal. i know only one person that liked the IV. personally i think it's crap. and you don't really need it for 6 months. man i can't believe i paid 500 bucks for an online program with a bunch of questions on it. that was so lame.