GWX has a deep and consistent research in the realism area, and I dare to say that not a single bolt in SH3 has been left untouched to improve that. However, the beautiful graphics and lots of contents added tend to outshine at a first glance the more subtle work in physics and realism. Yet beauty is not only skin-deep in this mod, as you learn by playing it more
I am more used to the NYGM "realism" aspect, but GWX has at least the same amount of research and changes -if not more- than that one (Which is usually taken as reference for realistic gameplay).