Linux, being a Unix operating system with loadable module support, is more appropriate for a server environment because almost all configuration changes do not require system restarts. Even insignificant changes to an NT configuration require or request a shutdown and reboot in order to make the changes take effect. To be fair, one should compare the NT server's performance to that of Linux or FreeBSD, since all three operating systems run on the same hardware, Intel. Unfortunately, a truly objective analysis of performance would have to based on benchmarks, but these are not plentiful and usually only focus on specific areas like Web performance. Also, Linux does not require a graphical user interface, while NT does.
Graphics require incredible amounts of disk space and memory.
The same holds true for sound files, so vital to Microsoft's operating systems. Actually, Linus is responsible only for the kernel. The whole OS consists of the kernel plus a massive amount of supporting programs and utilities written by other people. But, Linus holds the copyright to the kernel and the source code. Unlike other copyrights which are aimed at restricting distribution to commercial channels, Linus wanted Linux to remain free, and his stipulation to distributors is that while you may charge for Linux, you must ensure that the purchaser has access to the source code always.