I have a track record of being really open and interested in all racing sims and i own most of them, including iRacing. I have never said iRacing is "bad" or PCars is "better" than the other. That's a claim i leave to fanb0is all around. In fact, i have my gripes with all of them, but we must separate useless, uneducated chit chat from actual facts to be able to form educated opinions:
It is completely irrelevant for the "feel" of a track if its based on laser scans or not. Every track is visually modelled by the hand of track artists in a CG Software such as 3D Max or Maya and has no direct connection to the noisy point cloud used to get initial measurements. There are more methods than laser scanning available to aquire these inital properties (elevation, banking, width) of a track and every studio, including iRacing, uses highly simplified 3D geometries to keep the frame rate up.
On top of that, a invisible bump map is manually created to feed bumps and track properties into the tire simulation. The resolution of that bump map is just as hilariously rough compared to a real track surface as the 3D Geometry is (for every single racing game). The Quality/Realism of this Bump Map is equally dependent on the talent of the artist as the quality of the visual model is. Thats why input from drivers is important, it will add the important, recognizeable bits and bumps for realism to the simulation.
Laser scanning is one of the good, but slow and expensive methods to aquire real life reference data. For iRacing, it really is more of a marketing bullet point to convince people that their "Simulation Service" must be worth it. And it is, in the same sense "World of Warcraft" is worth every penny to the players paying for it. Users are confident this must be the only available real deal out there and are therefore happy to pay top dollar for outdated (Silverstone, Brands Hatch) or unfinished (Long Beach) tracks.
I'm really looking forward to the Assetto Corsa dream pack and will enjoy the "Laser Scanned" Nordschleife just as much as the ones from GT and PCars. And next time i take a skippy around Mid Ohio in iRacing, i will enjoy it too, mildly looking over all the flaws that come with it :-)