New Z06 has been stated (by GM) to be quicker around the track than the ZR1.
I'm not seeing any Porsche even close to the top of the list. The quickest Porsche is the GT2RS with 620hp and it's ranked at number 11 and the GT3RS is 19. ZR1 is number 2 and the Z06 is 5.
http://fastestlaps.com/tracks/laguna_seca.html
It'll be interesting to see where the McLaren 650S comes in since it's been vastly improved over the MP4-12C.
Also, the new GT3RS will be interesting. Again, it's going to be down at least 150hp from the Z06.