A word of warning — it's still recognizably Road America, but IMO, the version in PCARS2 feels slightly off, particularly in elevations. For comparison purposes:
IIRC, RA isn't one of the laser-scanned tracks in the game. And admittedly, elevation is a hard thing for any game to truly get across to the player. But as someone who only recently really became a fan of the track (originally hated it when I first tried it in Forza, now one of my favourites in that game), I wanted to point it out.
PCARS2 is a great complement to GTS. There's none of that hop-in-and-play feel that Sport Mode provides, but it counters with an engaging single player mode, and as
@Stotty said, the car and track selection is superb. Even with all of its updates, I'd say GT Sport's car list isn't quite as good (though it is arguably more varied), and no other console racer comes close to PCARS2 in terms of tracks. Both do different things very well indeed.
And yeah, track limits are much better now. I also prefer the game's penalty approach; if you do breach the limits, a warning to let any cars past that you took spots from is more straight-forward than a "slow down" message that doesn't give you any indication of how slow it really means.