Been covered before, some reviewers love the 370, others don't.
I am sure the Cayman is the better drivers car but for me the zed has character, is far more unique (caymans and boxsters are two a penny around here) has way more power and comes with a great forum community and some brilliant mates. If its the whole package for me there is very little out there to touch the zed for the money. Its the same reason i fell for the 350z.
Went to a friends bbq this afternoon and parked out front. Everyone saw and commented. Took some people out after they asked and it put a huge smile on their faces. Roof down, sun out, glorious sound. Was awesome and reminded why i love the car. Its about the whole package.