Ultimate Porsche track battle: Cayman GT4 vs 911 GT3 RS

Can the mind blowing Porsche Cayman GT4 live with its bigger, more expensive brother, the Porsche 911 GT3 RS, on track? Watch as Steve Sutcliffe finds out on the famous Silverstone National Circuit... Porsche Cayman GT4 review: Porsche 911 GT3 RS review: