I test drove the Cayman GTS and the 911 GTS and loved both. The new Cayman is so much newer, more refined, and more capable than the Z4Mc that they aren't even comparable on paper. That said, I don't think the Porsche is any more fun or engaging than the Z4Mc. The electric steering in the Porsche is great but not as fast or communicative as the Z4Mc, the S54 feels much more responsive than the flat 6, and the older Z4M just feels more mechanical and communicative.
My Z4Mc has coilovers, headers, etc, and I put a deposit down for a GT4 because I'm getting old and want a more comfortable car
