The fact of the matter is that all cars handle differently. A Miata will handle pretty closely to how GTA v driving is. A caddilac brougham will handle like gtaiv. It depends on the car and saying either is more realistic than the other really isn't saying much.
I will agree that sports cars from IV needed to be tighter, and I'm not saying IV was a perfect reflection of the real world, but it was far closer than V is.
You stick your toe down in a Miata and try a hard turn and see what happens, V reckons it will stick like it's on super duper slicks (rails more like) which is not true.
Equally drive the Brougham like Emperor in V and see how it drives, you can't tell me V has it closer to real life than it was in IV with a straight face