Linux is a VERY powerful system. So is Windows. If you know what you're doing in EITHER of them, they BOTH can be VERY stable systems. I've had Windows Servers that (patching not withstanding) ran Exchange, IIS, SQL, Virtual Machines, File, and Print services for a domain that ran without reboot or problem for 10 months (and I rebooted it only after mistakenly believing I was having a problem with IIS). And I've heard of and seen linux systems that remain booted for months and even years as well.
What you should use is what YOU know. Running linux is free of LICENSE FEE, but it's NOT FREE of support costs. Further, the linux community is fond of telling you about it's great support - and it's true - it's great support for THEM. When you try to ask for help from the Linux community, TOO OFTEN, you get back unhelpful answers that include "RTFM". Jerk, if I had time to RTFM, I wouldn't be asking the question!
I've setup linux a few dozen times and whenever I've tried to use it to any serious extent, I've eventually broken it trying to push it and been unable to get it working again even with the help of my local linux group.
There are other things to consider: For example, if you have Windows Workstations, you can implement some serious management capabilities using Windows Servers. Linux can provide centralized domain style logons, but cannot provide the fine tuned control over Windows workstations that Windows can.
Finally, I like to describe Linux and Windows (and Mac) like this and most people don't disagree much with the analogy:
Mac: Easy. Because, in general, there are only 2 or 3 ways to do anything in particular. When you ask for help, you get the same general response from everyone so learning it is fairly easily and quick.
Windows: Moderately difficult. Because there can be 6 or 7 ways to do something... As a result, you often get different answers which makes learning things more difficult to learn. It can make it more powerful, but more difficult.
Linux: Difficult - because you can ask 30 different linux experts and get 30 different answers on how to edit a file. There's a ton of editors, some for the command line, some for the Graphical environment. so while it's very powerful, it's extremely complicated.