On your 4 criteria above the Carrera is a definite YES=better.
The Cayman/Boxster drives more naturally due to friendlier handling. As soon as you drive one you feel at home. The Carrera needs an acclimatisation period and sometimes it reacts strangely especially the light front end.
In the wet especially standing water I find the Carrera better, whereas the mid-engined car can get light due to less weight on the axle.
Personally I find the Boxster a better option than the Cayman or the Carrera cabrio. If you want closed cabin go Carrera. If you want open top go Boxster.
Well my opinion!