I work in the medical industry. We have a mixed shop with well over 1000 Windows servers and well over 700 Linux servers--if you count clusters as one server.
We standardized on Red Hat as they do support Linux--though we only need to call them (maybe) once per year. Our Linux servers perform better than the Windows servers. We have fewer people supporting the Linux servers for a few reasons--we can do more than the average Windows admin, and the Linux servers do not need as much maintenance as the average Windows server.
In our case, Linux is very practical.
Generally speaking the above is true. Where reality parts with the above statement is when both Windows Server and Linux (in our case: Red Hat Enterprise Linux) are both run in a heavily regulated industry such as Financial Services.
We have @ 4,800 Windows Servers as VM's running under VMWare and @4,200 Red Hat Enterprise Linux servers also running under VMWare.
I'll tell you point blank that the tools to patch Microsoft Windows Servers are far more mature and effective in reporting patch status for example, than Red Hat Enterprise Linux Server is. The difference in the toolsets to maintain both platforms is like night and day.
Hopefully solutions like Chef and Puppet which are being positioned to manage both can handle both platforms as we move to a private cloud solution w/VCE. It would sure be nice to use one Enterprise Class management tool that actually works for both.