Without having any first hand experience, the claim is that it has a much larger sweet spot. Which was always the biggest issue with the G2, to be honest. On the other hand, every headset claims to have a large sweet spot these days, and that might actually be true for pancake lenses...I'm terms of image clarity, how good is Pimax compared to G2?
In terms of per-eye-resolution, it's got quite a few pixels more than the G2 - 2880x2880 compared to 2160x2160 of the G2. But in the real world, taking the need for oversampling due to the barrel distortion and the like into account I can't even push the G2 at full resolution with my 5900X/3080Ti. I run mine at 50%, and while going as high as 80% yields a small image improvement, it's barely noticable due to the small sweet spot of the lenses.
So I think it's the quality of the lenses that makes or breaks a headset more than its resolution.