If you happy with linux, stick to it. I think I would refuse (or simply stop) supporting our school's moodle server if someone told me to move it to a Windows OS. I used to run large heterogenous networks and the amount of extra work keeping a Windows machine happy and well fed is only worth it if someone is paying you big money to do it. The end users don't really care what OS the servers are using, as long they get what they want. Security is another point. Keeping your moodle on a separate OS and machine will increase the diversity of your network. Yes, it means you have to do a little extra work, but when the next big virus/hack hits your widows/linux boxes, hopefully only one type will go down. Presently you can run enterprise level backup, print serving, content filtering, messaging, telephony, databases, etc., all with Open Source and save a huge amount in license fees. And the security tools (snort, nessus, ethereal to name just a few) provide protection for all systems on your 'net. And unlike a Windows box, you can run more than one or two services on one box. My crappy laptop was running 2 moodle servers, MySQL, Postgres
, SchoolTool, SchoolBell as well as security scanners and 2 versions of Ubuntu while I was testing out stuff.
You said you have some other members of your team who are able to do linux. Great! Convert more if possible. There are some things that simply have to run on Windows, but Linux is becoming more and more useful, so I would try the professional development angle as well. Many of the students I show a linux server (or laptop) to are impressed and want to learn more. Having linux admin skills as well as Windows would be a wonderful addition to any CV.
And I have had experience with Red Hat, Fedora and SUSE, as well as a number of other *inux systems. For easy of use (I am an exceeding lazy sysadmim) I've settled on Ubuntu, as the installs and package manager software are just click and play. Took me all of an hour or two to set up our moodle server from bare metal.