Hi sjain263,
AndrewN has provided a proper description of how those books vary from one another, so I won't rehash any of that here.
Based on your initial post, it sounds as though you are thinking about taking a "book heavy" study approach. Unfortunately, many people who study in that way end up getting 'stuck' at a particular Score level. Even the best books are limited in what they can teach you; they also can't force you to approach questions in a certain way and their explanations are often one-sided. In addition, while the OG books are great sources for practice questions, they're not designed to teach you Tactics, patterns or the little 'secrets' behind the GMAT - for those, you'll need Course-oriented materials.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) Have you put in any notable study time yet? If you have, then how many hours do you typically study each week?
2) What study materials do you currently have access to?
3) Have you taken any CATs/mocks yet? If you have, then how did you score?
Goals:
4) What is your overall goal score?
5) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich
760+: What GMAT Assassins Do to Score at the Highest Levels