Well, with the Steam refund policy, I guess I could, at some point, purchase a copy of PCARS 2. I consider the original PCARS to be a complete waste of money due to the awful physics and FFB. It's a game I really, really wanted to love, but ultimately couldn't even play because of the poor foundation. It probably won't happen anywhere near game-launch, but if I get a chance I'll definitely come back and put in my 2cents worth... (But, as usual, I'll only be comparing classic-era rear-engine Porsches, because that's all I have extensive IRL experience with. Still, if you can't get the physics and feel of those right, you almost certainly can't get anything right, because those handle an extremely specific, easily "feel-able" and unique way.)
So I finally had a chance to purchase PCars 2 and spend a good amount of time testing it within my Steam return window.
The bottom line for me is that I returned it. I really couldn't give it a proper test vs. real life since they don't have a single digital equivalent to my RL cars (why, why did they remove the YB? That's crazy!) So, I can't give a direct AC vs RL vs PCars2 comparison.
What I did do was use the modern 911 GT3 RS, which I've driven a lot in AC, so at least I would be working with the same car. IMHO both the physics and FFB of PCars2 is vastly, vastly improved over the atrocious PCars1. Still not as good as AC, but certainly pretty decent. If forced to exactly specify why, it's because PCars2 doesn't feel as "connected" or "accurate" as AC, but unlike PCars1 I could at least tell, for example, that I was driving a rear-engined car. I tried all three profiles and many setting adjustments, and in terms of physics/ffb guess I would give PCars2 a good solid "B-" and AC an "A" (in comparison PCars1 was, in my book, a D- if I'm being generous). AC definitely gives me a better sense of what my car is doing, but PCars2 is at least decent. My main complaint about the PCars physics and ffb is the near complete lack of understeer feel through the steering wheel, something AC does very well. In terms of weight-distrubution & transfer, this is far better in PCars2 than it was in PCars1 (where it basically didn't exist), but AC still has a definite edge in my book.
In terms of graphics, obviously PCars2 has a lot of eye-candy that AC lacks. And the different weathers, surfaces, and times of day in PCars2 are things I would love to eventually see in future versions of AC. Interestingly, in terms of overall fidelity I think AC has the edge, probably because it wasn't originally designed with console limitations in mind. Cars retain far more detail in the distance in AC, for example, than in PCars2 where they pretty quickly become lower- polygon blobs (my system can run both games at 2560x1440 with essentially all other quality settings maxed, so I'm not running lower setting on PCars2 or anything like that). I really expected PCars2 to outshine AC in all areas graphically, but of the two, if forced to choose, I prefer the overall fidelity, sharpness, and distant-rendering quality of AC over PCars2's (very fun) eye-candy.
But despite all the very good things about PCars2 (weathers, time-of-day changes, multiple surfaces, eye-candy, look-to-apex function, etc.) I ended up returning it because a) the physics and ffb, while pretty good now, just aren't up to AC's quality yet b) PCars2 has very, very few cars I'm actually interested in driving (I drive classic-era cars probably 95% of the time in racing sims) and c) the PCars2 AI is like something out of GT4. In AC you can watch the drivers around you actively trying to avoid collisions, both with your car and with each other. AC does a pretty good job of this, and most of the time if there is contact it's because I've done something stupid. PCars2, on the other hand, no matter what AI difficulty and aggressiveness I used, repeatedly rammed me, especially from directly behind, often as if the AI car didn't even bother to slow at all. It really did feel like stepping all the way back to GT4. What a bummer on that front.
I'll definitely revisit PCars2 at some point in the future, either when it's gone on significant sale (If it was a $39 game I would have kept it), or when they add more cars I'm actually interested in driving. I would freaking LOVE cruising around the ring, in the winter, with snow accumulation, at night, in a blizzard, in the Yellowbird, or a Stratos, or an Alpine A110 (either old or new), or any number of other cars which aren't yet part of PCars2...