Compared to the OG Verbal, the test questions are clearly more difficult. That book is just too easy and needs to be revised. But there isn't a huge disparity between the OG 12 or GMATPrep and the real test. The test questions are more challenging, but not to the point where this will throw you off considerably.
The best defense against this is to re-read the verbal guidebooks to make extra sure that you're fully prepared (trust me, going through those books twice or more helps). And I would actually advise you to look into LSAT RC passages. Those are quite helpful. I also can reccomend the LSAT LR questions, though those aren't as good as the RC passages.