best wing for a coupe?

I like wings and all, but i wonder do they do anything besides adding 5-10 lbs to the vehicle weight. The saleen is nice but i dont know which is like better, wing or wingless.
 
A wing is useful if you are driving on a road course or just like taking fast corners. The problem with most wings is they actually generate lift because of their poor design (aka they are for looks). Most people running a rear wing and front splitter/air dam have no actual technical knowledge regarding how much or how little drag and actual downforce are being placed on the chassis. A wing is for fine tuning a chassis and the only way to do this is in a windtunnel or at higher speeds (i.e. 130mph or higher, where slight changes are obvious).

HP Motorsports makes one of the few useful and wind tunnel tested wings for mustangs. I've had one on my race car for a year now and I can DEFINITELY tell you when it's working properly or when it's not. The 93 cobra we installed it on is like a jet boat in a hurricane at 130+ without the wing. The difference is real, but most people use them to make up for their lack of power and suspension.