Absolutely! A Cayman R isnt much slower (traps ~111 mph), and the handling, balance, suspension geometry and precision of it is on a completely and utterly different level than our M3s (have a friend who owned a Boxster Spyder and now has a Cayman R). There is no comparison as far as handling goes. The Spyder and R are world class performers on the track and off. Handling-wise, they are right up there with the best, the GT3/GT3RS/GT3 RS 4.0.
As far as the Z4M goes, it cannot compare. Even a 2006 Cayman S Gen I dominated the Z4M Coupe or Roadster in every aspect and the Spyder and R are again far, far above that level.