Re: Z4 Coupe
I found this Z4 Coupe to be possibly the best driving car BMW makes today. The list price is at S$209K which in my opinion is a FAIR price but it is not subject to super big negotiation because it is a niche model.
I agonized over it and decided to spend S$30K more on a Cayman. Don't get me wrong, the Z4 out HP, out Torque and out speed the Cayman in a straight line, but the sound of the Z4 coupe is not as exciting, and the Z4 Coupe noticeably understeers a little bit on medium speed corners - ie the Cayman handles better - it is neutral while the Z4 is default understeer behaviour. The Z4 3.0 Si coupe does allow trail braking where the Cayman allows LESS trail braking, if you trail brake too much in the Cayman you will feel the rear end slide a bit.
The engine in the Z4 SI coupe is superior to the Porsche flat6 2.7 in every way save sound. Low end mid end the BMW aces it, though high end the Cayman 2.7 seems to pull better while the Z4 Coupe 3.0 seems a little flat ....
On a more academic note (because you'll never usually notice it until your engine grinds itself to death) the Cayman has dry sump lubrication where the Z4 uses the more conventional wet sump. Theoretically the Cayman will be more suited for the track on super sticky tyres (think Michelin Cup, or more than 1G type sustained cornering).
The Cayman comes with PS2 or CSC3, where the Z4 the moment it comes you have to chuck away the runflats replace with some other tyre.
The Cayman is a substantially lighter car on paper, and you can feel it. The cockpit of the Z4 Coupe is slightly boring, the Cayman even in base spec looks a little more interesting and special. The plastics are nicer on the Cayman. The Cayman has more luggage space (2 golf bag no problem) where the Z4 has less. The interior of the Cayman is bigger than the Z4 by quite a lot in the subjective sense.
Exterior - the Z4 coupe is full of drama, and it aces the Cayman.
So, if you want the driving experience, go for the Cayman, everything else the Z4 Coupe aces it. Even WOW factor, the Z4 Coupe is more WOW except for the Porsche badge.
Racing fans - you'd probably feel better with the Z4 Coupe. BMW supplies the Z4 Coupe in THEORY to customers (though their list is very very short compared to Porsche's 997 Cup) but Porsche refuses to make any racing Caymans. And the Z4 Coupes under some customer teams are doing really really well compared to the 997 Cup, but maybe not the 997 GT3 RSR. New races like dubai Autodrome etc, all won by the Z4 Coupe R.