Pricier Sibling: 911 Carrera
Sibling MSRP: $89,400
Why it's better: Porsche is understandably beholden to its most loyal and well-heeled customers, who demand nothing less than a 911 with an engine in the very back, where it has been since day one. The marque's dirty little secret? In terms of performance -- which is kinda important in a Porsche -- mounting an engine in the middle (behind the driver, but in front of the rear wheels) makes for a much better solution.
Conspiracy theorists have claimed that Porsche deliberately holds the Cayman back, lest it embarrass its ultra-iconic older sibling by actually being faster around a race track. But then, the GT4 was born. It's cheaper, lighter, more powerful, and generally such a threat to the current 911* that Porsche won't even let you compare the two on its website's comparison page.
*Porsche recently announced its next-generation 911, with significant performance upgrades. Pricing is not yet available.