Lots of interesting discussions on this and as you might notice by reading them it is akin to religion. Everyone has a passionate favorite. Read the couple of hundred threads that already exist and see how confused you get....So your best bet is to try a few brands and pick what you like best. You can also read about claying and polish in many different threads. Do your homework and try some different products.

(Against my better judgement about recommending a specific product I will since you asked. For my silver Cayman S that is going to stay in my garage a long time it is P21S. Easy on and easy off. Needs about four applications a year. And you can get it from our sponsor Chris at Glimmer Glass Welcome to Glimmer-Glass Detailing who is a great person to deal with)