I don't have a gaming PC or an XBone. I have an Xbox 360 and Wii, but I didn't upgrade them because my kids have grown up and "grown out" of video games and become obsessed with their smart phones instead! I upgraded from PS3 / GT6 to PS4 / Project Cars 1 and love the game - so much better than GT6 in virtually every way that is of importance to me.
For me Gran Turismo is going in completely the wrong direction with its focus on E Sports in which I and my friends have zero interest. If it was GT7 and the premium car models were ported over and a bunch of historically significant cars were added I would have pre-ordered it even with the strong likelihood that sounds and AI will be poor in comparison with Project Cars, but GTS holds no interest.
I've tried the F1 games and didn't enjoy them - I like the direction they are going in now with the classic content, but for me it is not old enough - If they added pre-wing era F1 cars like the Lotus 49 and a personal favourite - the Gurney Eagle Weslake (which is in Forza) then I would buy the game.
I will be buying Project Cars 2 - the sounds, AI and (something important for me) the tactile effects for my Buttkicker and bass shakers are in a different league from GT and the classic / historic content is present and correct and expanded from PC1. I can't wait for September 22nd!