I don't think there's any question that an automatic transmission will yield more consistent straight line acceleration versus the average driver with a manual transmission.
Whether an automatic transmission is simply faster than a manual in general is another question. Other than shift speeds, the power robbing torque converter should be taken into account. Modern automatic transmissions shift very fast and the torque converters are becoming more efficient, but it still takes away some power.
In terms of the an auto versus manual 370Z, well gearing should be taken into account. The automatic is geared more aggressively in the lower gears compared to the manual, so other than shift speed, I think that's where the main advantage is. On a road course however, with an experienced driver, the manual should prove to be the better alternative.
These debates never end though. No need to defend what you drive or what you prefer. For myself, I'll always take a "slower" manual over the dual clutch and automatic transmissions out there.
