gujukrish
I am trying to decide between Empower and Optimus Prep. (looking for PEER replies)
Both companies have raving reviews.
Any tips or suggestions to sway me either way?
Also, has anyone ever taken the Optimus Prep CATs? How accurate is the score relative to the real thing?
Obviously my suggestion would be biased here

I would encourage you to take a trial of our course and of the live tutoring provided by us before opting for a course.
Since you are just starting with your preparations, the following tips might come in handy.
You need to build the concepts/fundamentals before you jump in solving the problems. You can do so by choosing one of the following ways:
1. In person classes/private tutoring
2. Online classes
3. Self paced online preparatory course
4. Book heavy approach
Whatever you choose, make sure that you choose one. Because GMAT tests you on some concepts and fundamentals that you can learn from a course. Most of the preparatory companies including ours offer a free trial of our course. You can take the trial and see if the course suits your needs.
In addition to the preparatory material, buy the Official Guides(both the Official Guide and the Verbal Review), Question Pack 1 and the 4 official mock CATs. They should be an indispensable part of your preparation.
You need close to 3 months to prepare well for the GMAT.
1. Understand the concepts and fundamentals before jumping into problem solving
2. Solve full length CATs including AWA and IR. You can get two free GMAT Prep mock CATs and can purchase two more from mba.com
3. Make sure you solve the official questions from the Official Guide
When are you planning to take the GMAT?