Because HRTF algorithms rely on a trick in order to work, we have tried to explain this to you but you refuse to listen. The algorithms are calibrated using average values, average ear sizes, average head size, average cranial density (might explain why it doesn't work for you) etc... If you deviate from those values the vss might not work (because your brain is used to your own morphology).
Again, learn to fcking read:
https://en.wikipedia.org/wiki/Head-related_transfer_function
And yes, the GSX is better than the rest because it adds no unwanted reverb and the HRTF algorithms are the most accurate ones on the market when it comes to positionnal audio.