With whatever knowledge i have from my acquaintances, I believe that NO in person coaching center in NCR region has a good track record for improvement in verbal.
BTW, Why are you restricting yourself to coaching centers only, There are so many international test prep companies who give online coaching. Why don't you check out the reviews in the review section, check out this link http://gmatclub.com/reviews/?fl=menu
Also, take a practice test to know whether you actually need coaching, may be you're already near the desired score that you want, ...So taking a practice test is highly recommended but before that know the test, know what all is tested, see few practice questions and take a test.
Good luck and Bon Voyage on the gmat journey.
Fire the final bullet only when you are constantly hitting the Bull's eye, till then KEEP PRACTICING.
A WAY TO INCREASE FROM QUANT 35-40 TO 47 : a-way-to-increase-from-q35-40-to-q-138750.html
Q 47/48 To Q 50 + the-final-climb-quest-for-q-50-from-q47-129441.html#p1064367
Three good RC strategies three-different-strategies-for-attacking-rc-127287.html