Hahaha. Its just that after being raised on Tolkien and Lewis and then reading about 100 Forgotten Realms books in middle school, it was just about time that I needed a change. Thats not to say that I read any fantasy book that is a "darker" (and I prefer greyer than darker). I think that Lawrence, Brett, Weeks, and Scholes are all very poor attempts at doing so. I still read traditional historical fantasy (Mark Hodder and Felix Gilman are my favorite here) and historical fiction (Cornwell is my favorite by far, followed by Penman). That being said, I do enjoy the morally greyer books of Cook, Lynch, Morgan, Scalzi (Old Man's War and The God Engines), Martin, Abercrombie, Abraham/Corey, and Bakker the most. On the other hand, I still read all of Sanderson, Rothfuss, and Hobb's books and those are all much more traditional.
All in all though, it comes down to the writing and every author has his or her's weakpoint. Hobb is strong on characterization but has a glacier pace. Lynch's first novel was great, but it appears that it might have been a fluke when you consider his second novel. Abercrombie is great on humor, woldbuilding, and plot twists but he has uncomfortably awkward sex scenes. Martin's books are near flawless, but he takes forever to write a novel and might have to extend the length of his series again as there appears to be too much that still needs doing...oh, and he might die before finishing the series.
So, I guess my point is that: no, I wouldn't say that greyer fantasy is better than traditional black and white fantasy novels, simply because it is greyer. Rather, that it comes down to the writing; however, if the writing were on equal terms in both types of fantasy, I would prefer to read the greyer one.
I hope that makes sense (its the night before my second advanced financial accounting midterm and I really can't think of anything else ).
Cheers!