Looks like the 350z coupe (not roadster) is a .2 seconds faster 0-60 (per wikipedia) but see attached picture

Also, Boxster has near 50/50 weight distribution and would do much better on a track anyways.
The s2000 is another story though, I was looking and those before deciding on my 986 (base model)
::EDIT::
I hate the way the 350z shifts, the syncro-match on the 370z is weird too!