991 Carrera (PDK) comparison with 997 GT3 (manual)
I was fortunate enough to spend the weekend driving a new 991 Carrera PDK back-to-back with a 997 GT3, which are currently available at a similar price. Here are a few comments on the 991 Carrera PDK with a focus on the gearbox...
Chassis -- the 991 is starting to feel less rear-engined and a bit more mid-engined, very impressive in the corners... almost like a Cayman.
Steering -- less feel than hydraulic steering in the 997, but still good feedback on dry road surfaces.
Brakes -- very strong steel brakes, as you would expect from Porsche.
PDK in Standard mode -- decent for driving around town at low speeds, or cruising on a motorway, but annoying elsewhere. Too much elasticity in the response to driver inputs.
PDK in Sport mode -- better than standard mode, with less perceived elasticity, but still changes gear far too often.
PDK in Manual model -- generally does what you ask it to do (like a Playstation) but not as rewarding as a traditional manual gearbox with three pedals.
PDK buttons vs paddles -- the standard buttons are ridiculously poor; paddles should be standard for PDK, with buttons an option for old Tiptronic customers.
E-Brake -- terrible, awful, pathetic, horrific, a big step backwards -- Porsche should reinstate a standard hand-brake as a priority! 
Auto Stop-Start -- not appropriate and annoying on a Porsche 911, so switched it off for every drive.
Auto Coasting -- not appropriate and annoying on a Porsche 911, so switched it off for every drive.
Interior -- notable improvement in quality, but some switches would be better of as dials (e.g. Sport button, Auto Stop-Start, etc) so you can keep it in the preferred position. Good iPod connection via USB input in glovebox.
Engine -- good improvement for the 991 Carrera compared to the 997 Carrera, but not a touch on the (more expensive) Mezger motorsport engine in the 997 GT3.
Sound -- ok in standard mode, better in sport mode. Engine noise piped into the cabin sounds a bit synthetic and obviously not a touch on the sound from the Mezger motorsport engine in the 997 GT3.
Traction -- good traction from standstill, but PDK does introduce a short delay before responding (not present with a manual gearbox). PDK may be quicker with launch control activated, but in normal driving the manual can be quicker to react from the lights.
Rear seats -- good rear seats in 991 Carrera / not available in 997 GT3.
Overall, the 991 Carrera PDK provides an impressive breadth of talents and certainly represents a significant step-change from the 997 Carrera.
The latest version of the PDK gearbox is an impressive development of the technology and makes the 991 easy enough for your grandma to drive. However, the PDK does change the character of the car and in "standard" mode you will often be driving in a gear that is 3-4 higher than you would with a manual gearbox (e.g. driving at 40mph in 7th gear). In "sport" mode PDK you are often driving in a gear 2-3 higher than you would with a manual gearbox. PDK hence changes gear much more often than is usual with a manual gearbox.
A drive in a 997 GT3 further emphasises the unnecessary number of gear changes in a PDK -- for example, 3rd gear in the GT3 is good for over 100mph without hitting the red-line. Furthermore, if you enjoy perfecting "heel-and-toe" gear changes, PDK will not be as fulfilling or enjoyable to drive.
However, if you are looking for a sports car that is easy to drive, PDK will be a popular option. The fuel economy that PDK can achieve is also impressive -- although I've never met a GT3 owner that complained about fuel economy! 
One of the attractions of a GT3 with a manual gearbox is that it is a real thrill to drive at any speed -- even driving around town at 20-40mph is a pleasure with that awesome Mezger motorsport engine singing through the revs and the chance to blip the throttle on downchanges.
This video by Chris Harris provides a good illustration of the attractions of a GT3 with a manual gearbox, compared to a couple of competitors with automated alternatives...
...yes, the GT3 RS 4.0 manual is faster and more fun to drive! 
In conclusion, I would suggest any potential 991 customer to test drive in a 997 GT3 and see which you prefer to drive!
Good enough for you? 
The GT3 still needs a good driver to be fast, you can't put a crappy driver in a GT3 and by magic, he is fast. 
I actually think that the new cars are more challenging because they allow the driver to experience the limit at a much higher level in a safer environment. When the rear comes though...well...it comes... 
