With regards to the Cayman comparison I think Nissan are being a little unfair. They're comparing the Z to a car Porsche no longer make, a pre-2009 2.7 Cayman. The current model is a 2.9 Cayman and even then I think they should really be comparing to the 3.4 Cayman S. Then the stats wouldn't work in Nissan's favour of course
Still love the Z though