They are 3 different books. (though the verbal one overlaps a bit with the Kaplan Premier
It is similar to asking if you should wear pants or just shoes and a shirt
If you already have pants (CAT tests and general gmat knowledge) then sure, just get shoes and a shirt (2 Kaplan
workbooks) - otherwise all 3.Kaplan Premier
comes with 5-6 CAT Tests and some good review for quant and general test strategies.
Founder of GMAT Club
Just starting out with GMAT? Start here... | Want to know your GMAT Score? Try GMAT Score Estimator
Need GMAT Book Recommendations? Best GMAT Books
Co-author of the GMAT Club tests
Have a blog? Feature it on GMAT Club!
GMAT Club Premium Membership - big benefits and savings