never had the 370Z winning. That would be my answer. Now whether there is enough of a difference to justify the price difference is another story...one you and I may answer differently. But go to the comparisons and you'll get list of high and lows.
http://www.roadandtrack.com/article.asp?section_id=10&article_id=7659
The short answers...noise visibility, handling, balance and refinement.
Not that the 370Z isn't a nice car for the $.,