Does AC really have that much better physics that you'd make the switch?
Regardless of how "far advanced" or "evolved" Asseto is over NetKar Pro, it's easy to understand where exactly does Asseto stand if you pay attention to posts/articles/presentations of Stefano where he presents his own views on NetKar Pro and Asseto (and where he himself believes each should fit into).
First of all, if you want to have some clear understanding of what you ask, strip away HYPE - hype from supporters, hype from those who plan to take profit from these sims (and I'm not talking about developer studios), and hype from the marketing heads working their brains out to sell the product (the sim).
Strictly speaking from the perspective of people with very much relevant knowledge/experience of both simulations and race car driving/engineering, are the
differences in physics (between iRacing and NetKar Pro and Asseto Corsa, or any other sim) that big or obvious to make it worth the switch? No.
Not worth to make the switch from rFactor/GSC (older platform) to iRacing or Asseto Corsa, and certainly not worth abandoning the best online-racing service in the market today (iRacing) for anything new.
Obviously, that's "just" the feedback I got from those involved in motorsports (and simracing), the kind of feedback which for some is unimportant.
I'm relatively new to sim racing, granted, but I find iRacing's emphasis on physics really exemplary
They're really emphatic about laser scanned tracks, the "plug and play" nature of the sim, the structure of online racing, FIRST and...continuous development.
Physics has always been the subject of much heat and controversy, even among iRacers, and even more so after the release of the NTM. Two years have passed since then and we're still discussing and having to deal with odd issues or inconsistencies between cars (and often, between builds of the same car).
I don't doubt there's a will to strengthen the "emphasis on physics", but there's too much going on at the same time (new cars, new tracks, more users, maintaining two tire models at the same time) for that to happen soon.