Performance statistics

Without asking for any blood letting, I'm wondering if there are any hard statistics available to prove  if  Windows Server is faster than, slower than or the same as for performance to one of the various Linux distributions.  While our application is a commerical application, in our survey we've been asked for information on running the server on a Linux box vs a Windows Server.

I suspect that running on a Linux server will be faster, however I'm concerned about maintenance at customer sites who have no Linux support and are a Windows based shop.  The application is written with a Windows based language. We will also be hosting smaller companies so I want to see the statistics and if Linux is a clear winner, the best distrubution to work with.

Best Regards