Choice of Web server platform

Dear all,
The company I worked with is now considering implementing a private 
IP network with Web servers at major cities. There is currently a debate
on what Web servers to use.

For reasons unclear, the majority favours NT. I am the minority who believes
UNIX based servers like CERN or NCSA should be used because
1.Field proven
2.Many ISPs uses it
3.A lot of CGI-BINs, statistics collection tools around
4.Support caching ??(does NT server do the same ?)

Could anybody advise if there is any paper on this ?
Could anybody with experience in either side give their advice ?

Many thanks
Kevin