Although I haven't fully driven every car in AMS2 there certainly seems to be a pretty big range in quality from what I am experiencing. From what I have driven:
Favorite:
GT4. These are just incredible to drive and they feel different from one another. They can be as safe as you like with TC and ABS, or turn them off to wrestle the cars around the track and really have to manage throttle and brake. REALLY enjoying these. The one knock is that the Camaro does have floaty steering.
Stock Cars. These feel like the perfect league car. Very believable and a lot of fun. P2P adds a nice strategy element to races. All the different years feel very good. They seem to have a little less of the dart-ish behavior that made them less fun to drive before.
Honorable mention: Caddy Dpi
Least Favorite:
Pretty much every openwheel car. Honestly these cars magnify the issues that persist with this game that aren't as noticeable in other cars and for that reason they just don't feel realistic at all and I hate driving them. There is too much grip under the limit and too little at the limit. The result is not only poor immersion, but snappy and annoying behavior. The other issue is that turning the steering wheel more gives you more grip/turn in. This just isn't realistic. Combine that with the fact we only have the softest and grippiest compound and it just kills my immersion.
Agree with everything here definitely - but the more I search the more I can grudingly accept the feel of several cars, while a few seem top notch territory; though they would be let down by the progressing grip tuning perhaps somehow. And the fact that unless the game is on the highest grip setting its just simply not much fun to drive. The model falls apart and especially with the F1's its so glaring, that as good as the couple I mention below are, its passé; it just doesn't inspire one to return to the game overly much.
I would say this is one of the biggest reasons why I give this game the short-shift these days. At some point the open wheelers became horrible compared to how they used to be. They compound everything that is wrong with the game.
That is, apart from two. Gen 3 car1 and 3 iirc, its a turbo classic-modern and car 1...not the earliest ones, the middle ones. And not the reiza ones.
IIRC I mean the 1991 geoff crammond f1 grand prix type cars, from the microprose game. Thats how I remember. Those feel pretty darn good. Kind of like up there with an Assetto Corsa Williams mod car I am thinking of, from the same era, kind of up there. But not quite, it would be the AC mod Williams fw19. Obviously AMS2 is a long way off AC but the AMS2 cars I mentioned (or those I am referring to) are actually fun. I explain below that even then they are no substitute long term.
Even then they do not have the nuance of the other sims. But believe it or not they do move around the track fairly good. Its just the little things in between that the madness engine is simply not picking up. So while they do behave in an outline kind of fashion they simply do not colour in the picture so to speak. And only those two cars.
Totally flummoxing for a game billed as the pinnacle or culmination of a period of time, ten years.
This is why i think the game was made to conform to YouTube videos of track-day drivers - the cars copy the outline of how one races round a track but not the 'feel' of it. Its not my intention to offend, only convey
All other cars its difficult to say since they change so much. But even the group C which were/are a lot of fun lost a lot of their luster. So I can only ever limit driving many cars to certain tracks and not all cars. I won't touch the gt3's much if at all, maybe the bmw and merc thats it, and the group 1's are ok, but all feel flat.
The rocco is simply really good. Maybe a couple more p1's or p3's etc.
Its not the sort of game that makes you hold it highly each time you play it.
There are only so many times I can justify taking the rocco round nord 24 hours for example. The game is let down in so many regards. Bathurst has always been a great track in AMS2 but the cars one can barely bother to drive round it. And despite with Bathurst one wanting to take the GT3s around it, for example, you can't guarantee each month the gt3's are going to be believable.
Yes the GT4's are quite good usually, and the porsche cup can be ok, and the rsr porsche, gt1's, but they can also be flat, where you would want spritely.
So this is the problem. A very disjointed game with cars, a couple of standouts. Even then you need to be contesting a pretty close race to 'forget' about the blemishes as there's so many. It can be fun, but the cars are dire when you consider out of 120 of them, I only mentioned 3 or 4 I hold in high regard, which limits the utility of the game. Oh I also wish the Ultima was great again, if its so that would be good, but I doubt the game will be played this month and it could change by next.
And for some reason the stock car has never changed and always been good. The trouble is, look at the playing numbers - the least popular car to drive - and limited to a few niche race series round the globe - the stock car (nascar aside and those) is of limited value. As good as they can be, most people find them odd to drive.
edit: I actually use default progressing. I use default ffb too in sensible amounts. The grip is much better these past 2 months. But maybe the cars are never all or majority firing on all cylinders so to speak.
EG: driving the m6 bmw gt3 across all top games, the ams2 one seems stilted and jagged by comparison, almost as if its a static object! I even took it to AMS2's best track by far the nordshliefe dlc, GT Nürburgring track. Somewhere AMS2 has definitely missed a trick. The procar by comparison is very good - but that car is a veritable brick lol, the game suits it, and thats not saying much though it is definitely fun; but there's only so much one car can do in this class/style of race
- then switching over to the custom downloaded file prepared by the poster iirc with the kiwi bird for his emblem, that improves things but the cars do have glaring issues. at this point going back to the rocco made a really good race, but the f1s I mentioned well not as good im afraid; as good as his ffb file is, the BMW then seems like I am moving a heavy cube across the track!
You literally can't win with this game. 3 laps with the rocco and its starting to handle really lovely for the slidy mess that it is. 3 laps with anything else and you begin to wish you had a car bomb in the game and a cliff. Invariably you will be doing good in an intense race and just before the end, at 10 out of 20, on hard, the AI will clip you. And thats that. Its a good racing game for a select few cars (in a limited quantity type way even then but genuine fun), but ultimately also naff in many other cars in terms of driving and racing. 
