There are 2 main differences:
1. ISF CCC- Only matters if you plan on a professional calibration. Even then, it will depend on how picky you are if it will look any better than a calibrated GT50.
2. Screen Filter- The VT50 has a much better screen filter that will improve the picture during daytime/ lights on. To me, this is the biggest reason to opt for the VT50 over the GT50. Won't matter if you are putting it in a dark room though.
NHT speakers, Denon 4520, Panasonic 65VT50