Hi,
I have been preparing for GMAT.. well preparing for GMAT and preparing for CAT is preety different
The Verbal/English section in GMAT is much different from that in CAT, n is also difficult which needs dedicated practice n preparation. Although preparing for GMAT will help you in CAT English section
Whereas the Quant section in CAT is much tougher than in GMAT. If you're done with Quant for CAT, you are almost done for GMAT Quant as well
There is Data Sufficiency section in GMAT Quant, and smthing similar also comes in CAT
Hope this helps,
All the best