PCars 2 has already been announced and with no more crowd funding extra content, bug fixes etc will slow down for PCars.
Ah I wish people would spend years making half-baked games. Even though AC has less content, are there a lot of good, free mods like tracks and cars?
I object strongly to you playing "Mystic Meg" here, just because word got out that Ian Bell wants there to be a sequel, that does not mean pCARS will automatically be ditched in Codemasters fashion with lots of bugs.
We have had reassurance that pCARS support will continue for some time yet, as the sequel is not likely to be released for ~3 years or so.
If you want to practice for track days - Assetto, if you want a game with decent arcade physics- pCars. But ironically Assetto has a lot more choice in terms of street cars, 75% of pCars are racing contraptions. Laser scanned tracks and racing school grade sim physics (Kunos makes road car sims for Ferrari and also for ASCI racing schools in Italy) are more fun to me, but each to his own.
Project cars BMW 1M on Nords, note the lack of steering input:
Assetto - same car, same track - its a different experience by far, much more alive (and this example has track grip set to default unrealistic "Optimum" setting. For Nords, devs say that track surface should be set to "Old" and track temp to below 15 degrees. On that setting the car is more alive still).
So if you like to go fast and have fun - either would be ok, but pCars may be better. If you like to think about trailbraking, lift-off oversteer, and preventing snap oversteer - AC is the right choice.
Looks more like pCars to me than AC.
Project Cars if you want an actual game.
Assetto Corsa if you want a simulation but aren't worried about any actual game.
I find Project Cars much easier to play, by my logic that means it is closer to driving IRL.
I'm not sure if my logic is accurate, but I always struggle to play driving games which feel unrealistic because I try and drive the car as I would IRL, and it feels wrong. Project Cars feels much better.
It took me a long time to tune my g27 inside ProjestCars.... out the box it was bit naff, following the forum posts and after editing a few of the settings, on the cars i'v gained about 4 secs a lap. For me its better game but i didn't play AC for too long.