This is a somewhat common concern among members. The OG 10
has a reputation for its large number of practice problems. However, some of its questions may
overlap with the GMATPrep question bank. This could diminish the benefits from taking a CAT under realistic conditions. The OG 12
probably contains more difficult questions, although many complain that there is still room for improvement. I personally recommend the OG 12
, OG Quant
2, and OG Verbal
2. Along with the GMATPrep, this should be enough GMAT questions. Once you master these problems, you can move on to more difficult material.
And here are a few discussions that might interest you: og-11-vs-og-41523.htmloh-12-vs-og-11-difference-109764.htmlgmat-prep-vs-og10-104032.html