Just found the September 2003 issue of Road and Track. It contains a run-off called the "Convertible GT Comparison Test". The cars tested were the Cadillac XLR, Jaguar XK8, Lexus SC 430, Maserati Spyder GT, Mercedes-Benz SL500 and the Porsche 911 Carrera Cabriolet.
After testing and comparisons, the cars were ranked in the following order:
1 - Porsche (568.3 points)
2 - Cadillac XLR (551.9 points)
3 - Jaguar XK8 (544.9 points)
4 - Mercedes-Benz SL500 (542.2 points)
5 (tie) - Lexus SC 430 (531.2 points)
5 (tie) - Maserati (531.2 points)
For those curious, the hood opening times were:
Porsche - 16.5 seconds
Mercedes-Benz - 17.2 seconds (hard top)
Jaguar - 18.2 seconds
Lexus - 23.7 seconds (hard top)
Cadillac XLR - 26.7 seconds (hard top)
Maserati - 30.7 seconds
Andy