Some of the cars are just honestly generic filler cars, with a few changes or its a special color scheme and that for some reason warrants it being a whole separate car.
The first 3-4 Evos in the lineup have small hp gains with each one. I think EvoI was like 230hp, and by Evo IV it was 250hp. Other than that most Evos react the same to me, all with AYC. You win a special Evo in a one off color scheme, and it doesn't handle any better than any of the other Evos.
Imprezas are the same deal, but some of them come in coupe form (throwback!) so they are lighter, so technically they handle a bit better, but its the same deal as the Evo.
There is the GTR, with the '07 model, the V Spec, and the Black Edition '12. The '12 version has more hp than the '07 I believe and the V Spec is a lighter model GTR so it handles better.
Miatas are all the same, the PP, the hp, and the weight is all the same, even the price, so handling is exactly the same.
For Skylines, the Nur package has slightly better handling than the other Skylines, but most of them are about the same with a base 276hp.
For the NSX's, the Type R packages are stripped down versions of the base model, so they are lighter and that means it would handle better than the regular old NSX.
Rx-7s are the same deal, but I think the efini model Rx-7s get better handling and a feel than a regular one. (opinionated)
Last gen Supras differ, the RZ is a turbocharged one, and the other is not. More hp, and they are both standard.
Nissan Skyline Coupe and Infiniti G35 handle the same, with the G35 being cooler lol!
Silvias are the same generally throughout (S13-S15) but some are turbocharged while others are not, so its either more hp or not.
Thats all I can think of for now