I test drove the 4.8iS last fall and I am going to tell that the 4.8iS exhaust sound is much more aggressive and deeper than the 4.6iS hands down. You can hear it inside car and definitely outside the car. The best part is when you first start the 4.8iS....nice deep rumble!! Go the dealer and hear one yourself!! The 4-corner air suspension (height adjustable suspension is standard in the 4.8) is great in the 4.8iS and it rides and handles better than a non-height adjustable air suspensioned 4.4i or 3.0i with sports package.