Hi,
This is a very subjective thing. I tried free study materials for verbal in the beginning. But for the 700-level verbal questions, especially the CR & RC ones, I could not get much help out from the free study materials as you need some explanation in-depth for those questions. GMAT Club comes to the rescue most of the time for question explanation but on the topics where you are getting stuck, you may need to go beyond the free study material. That is when I tried egmat and find it quite useful. That is how I was able to improve my verbal score.
However, I would like to mention here that for me egmat worked, but for others, something else would have worked. So, in the end, it will be your call and people have their different opinions & experiences. I am unfortunately not able to tell you what is the best verbal coaching because calling out something the best is very subjective.
Practice, Strategize, Excel...
Hope it helps!