I fell in love with the 458 too, I also still find the F1 cars in this sim are my favourite and what I feel are closest to reality currently, it gets me excited about what is in store for the future, I would like to hope that we will get some Formula 1 or Ferrari action in Assetto Corsa, probably won't happen though sadly.
As for the KS2 vs FVA, I thought they drove very similar, the F1 car is more stable and has more downforce as I would predict. I think a lot of people confuse a car that is easy or natural to drive with being arcade, if you compare it to telemetry, onboard videos, and what can be learned about F1 cars through documentation or videos I think you might find yourself ending up roughly at where FVA is.
It is ludicrous how early and how hard the F1 drivers can get on the throttle, how they can catch slides and how late they can brake, especially with the 2010 cars with double diffusers and bridgestone tyres. F1 cars are easy to drive by design, and often enough hardcore sim racers like/expect difficult and challenging drives by nature.
Ask yourself, were you able to beat the times set by the F1 drivers? If so, how many laps did it take? I think the difficulty of driving an F1 car is more to do with the competition and skill of the other drivers, how fast they can adapt along with managing the brakes and the tyres, the wear and adjusting to the situation. It is these final things that simulations are lacking in, the real world variables. When it comes to driving the car in a simulated one lap (hotlap) driving model I think by current standards FVA is the best that is available to us.
Thats how I feel about it anyway.