I've never tried both cars, and my original thought was maybe getting an upgrade in the Dream Car section to a Porshe 911, Cayenne, etc.
The Camaro SS - Just because i've never tried it out.
In the past i've had:
Corvette C6 Conv.
Corvette C7 Stingray Conv.
BMW 650.
Mustang GT conv.
Mustang Shelby GTH.
Porsche 911.
C63 AMG
Regular Mustangs Conv.
GMC Yukon
Chevy Suburban
Cadillac SRX