I have played both and the only thing I'm sure is that I can't tell which one is "better" in terms of realism or hardcore. My opinion is that it ends up being a personal matter of which gameplay you prefer. Each mod makes decissions and takes options for each subject of the game, and while the end results are always good, they are somehow different.
GWX has however tons of eye-candy that NYGM does not ship, if that can be a factor for you (Positive if you like eye-candy, or negative if your PC struggles to run a modded SH3).
My advice: Download both, make dual installs and try yourself.
I personally played mainly NYGM, but it is a subjective and personal choice, and no way would I be dissapointed or unable to enjoy the game if I had to stick to GWX. Quite the contrary, but I have only one life and little spare time, and I ended up playing with the one I started with and was more used to.
