I think the cars and handling within the broader system are great. A lot of cars feel pretty unique. I think I've driven almost every car extensively now, and I get urges to drive so many different vehicles because they're so unique. The dirt road handling is pretty good, too. I especially like the SUVs and luxury cars in the desert, the body roll, suspension, and sound effects of the bumps are great. Especially the suspension, the luxury cars have pretty good weight and bounce through the dirt bumps, and the new 6x6 Dubsta is especially awesome for showing the suspension of different tires on different size rocks and bumps.
However, that said, the broader system is a bit arcade-y. I mean, it's certainly a lot closer to GTA IV than, say, Burnout or Ridge Rager. It reminds me a lot of old Need for Speed games that were a bit more sim-esque (not the new arcade racers).
But I do miss some of the weight and body roll of GTA IV. Sometimes IV felt too exaggerated... I race and offroad IRL too and even if there is that much weight and body roll, technically, you never 'feel' it... but in IV the 'feel' is pretty exaggerated sometimes (not always... I think SUVs were worse my SUV is never like that at the track lol) but muscle cars in GTA IV were pretty amazing for weight and body roll. And IV had killer acceleration 'feel'
so wish it was a bit more of a balance between the two games.