Its similar to step 1, but there are just so many more topics to cover in the overall subject matter. CB is good at getting you ready for comlex type questions though: best vs first vs definitive next step etc. I know people who have done cb, CQ, and uworld and people who have done only one of those. Their scores were all over the place between each other, but were similar to their step 1s. Do what you did last time, I'd say.