Found a little concerning post on Pistonheads :

Just curious, spoken to one or two with manuals and they are a little disappointed, in comparison to the pdk version they drove previously.

Reports that the car seems a little 'dialled back' compared to pdk. The engine spools and changes so quickly with the pdk, less so with the manual possibly to protect engine. Interesting.

Some other guy responded :

It's a given it will be down tuned

The PDK car was tuned to work with RWS and the e-diff from the off.

The manual was an after thought, has less RWS angles and no e-diff so it's a totally different tune in the manual car.

Hence why the performance figures are so far apart from PDK to Manual this time, normal it's a 2 or 3 tenths loss on the GT3 PDK vs manual you go from 3.4 seconds down to 3.9 seconds.

[...]

Can the manual cars really be down tuned ? Surely 911R owners, who have driven a 991.1 GT3 RS, can chime in and share their experience comparing PDK and manual yes