Just comparing Motor Trend data. In general, I've usually seen NISMOs at about 71 and 370s at 69 to 70. They are so close, it's really down to the driver anyway. Skidpads are usually something like .91 for the NISMO and .97 to .99 for the 370Z if I remember correctly. Sorry if I was being too "conclusive" :D

As I thought about it, it didn’t seem fair for me to ask what you are basing your conclusions on without providing at least a couple of sources myself so here goes…
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370Z TESTS….
RoadandTrack.com -- New Car Search - Full Test: 2009 Nissan 370Z (1/2009)
Skidpad: 0.97
Slalom (700’): 71.4 MPH
0-60: 5.1 seconds
0-100: 12.8 seconds
¼ Mile: 13.7 @ 103.6 MPH
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Comparison Test: 2009 Nissan 370Z vs. 2008 BMW 135i

EDIT: Now that I've read your reply, I see we were pretty much thinking alike!
Skidpad: 0.97
Slalom: 69.8 MPH
0-60: 5.1 seconds
0-100: ---
¼ Mile: 13.4 @ 104.6 MPH
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NISMO 350Z Tests….
Follow-Up Test: 2007 Nissan Nismo 350Z
Skidpad: 0.91
Slalom : 70.0 MPH
0-60: 5.1 seconds
0-100: -----
¼ Mile: 13.6 @ 103.0 MPH
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RoadandTrack.com -- Cover Story - The Fast & The Frugal: Nissan Nismo 350Z (8/2008)
Skidpad: 0.96
Slalom : 69.4 MPH
0-60: 5.3 seconds
0-100: -----
¼ Mile: 13.7 @ 102.3 MPH
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Obviously, testing differs with any number of variables but based on the above (as well as other articles I’ve read, it looks to me like the 370 has an edge in the skidpad, in acceleration and is almost in a dead-heat as far as the slalom goes…the 370 seems to have a nice edge in braking (60-0) too although I didn’t list those numbers.
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If someone is shopping a 370 compared to a NISMO 350; I’d say the decision is going to have to be made on issues other than the raw numbers and lets face it, regardless of which vehicle you give the nod to based only on the numbers, the numbers are so close that any “advantage” can easily be erased by driver skill (or lack thereof). :)

Not true. The car with the higher slalom speed means it's more responsive and will also stick better. The higher lateral G's is going in a circle and seeing when the tires just won't grip anymore. That has a lot to do with better tires.

The NISMO also does .98 G's in a test I saw not .91.

Nice post Nash. I didn't see the new numbers from R&T. So pretty much a dead heat between the two cars.

Edmunds got a .91
Follow-Up Test: 2007 Nissan Nismo 350Z

They got a .97 on the 370.

I can't find the motortrend review, just going on memory so it could certainly be suspect. :D As Robert says above, these numbers are close enough to be within the tolerance of driver ability.

On a dusty track like they said.