Almost every company worth their salt nowadays will give you an option between Linux or Windows for the operating system on your dedicated server. Debates have been waged endlessly on the Internet over whether or not Linux or Windows is the better operating system for your server, but the bottom line is this: for 80% of small business owners or mid-level traffic clients, it makes no difference what operating system is on your dedicated server. I personally prefer Linux on my servers, and I have used it successfully for quite awhile now. I don’t have as much experience with Windows server OSes, but the few times I have used them they seemed responsive and just as good at serving HTTP requests as their open source equivalents.
The astute reader might notice that I haven’t answered any questions- which OS should someone go with?
If you’re not developing any Windows-specific sites that use things like ASP or ASP.NET, I would go with Linux. Since the OS is free, the solutions tend to be cheaper monthly- just by peeking over at LiquidWeb we can see that the same dedicated server solution running Linux is slightly cheaper (189$ a month for the Linux setup as opposed to 209$ a month for the Windows setup- it becomes even cheaper considering you have to add 15$ on top of that if you want Windows Server Enterprise). CentOS also features a pretty easy server GUI that’s fairly user-friendly, and with the newest version of CentOS it’s just as easy to set up a web server using Apache as it is using Windows Server and IIS.
I’ll admit I may be a little biased; I use Linux more at work and it’s quite possible that I just can’t see the difficulties inherent in it. It wasn’t terribly difficult for me to pick up, however, and I had been born and bred on Windows machines all my life. I’ll close this up by saying it can’t hurt to run Linux if you’re not afraid of learning a little and aren’t running any OS-specific apps; that 20$ a month could be well-spent elsewhere!