So, tonight I did Z4 GT3 vs GT-R GT3 vs SLS GT3 vs R8 LMS Ultra... each at Motegi East, Eiger Norwand, Brands Hatch and Bathurst.
Conclusion:
There's really nothing in it times wise - except for the R8.. I gave up since I wasn't able to set a lap without coasting through many of the turns on each of the circuits - literally, 3 secs a lap slower at most tracks to avoid spinning!.
Overall, out of the 4 cars. The SLS is just so easy to drive, even though it was a tenth or so off the Z4.. over 10 laps or so I'm sure the fact that it just goes on and on without any drama would give it a decent lead. In comparison, the Z4 is a little quicker, but it's way too sensitive to undulations under braking. The Turbo nature of the GT-R meant that it would feel sluggish, right up until the point the torque kicked in and the back end started to slither- heavy but stable.
All laps completed Stock, using a wheel, ABS1, other aids off, MT, RH/RH.