I'm trying to figure out the difference between Linux and Unix hosting and the differnce between Microsoft hosting and Linux/Unix.
Geez... this is a can of worms
Linux vs. Unix
Linux = GNU = GNU's not UNIX!
But seriously, Linux is a UNIX-like operating system. It is "UNIX-like" and not "UNIX" because it does not conform to whatever the Single UNIX Specification is. The Open Group holds the copyright to the UNIX trademark while SCO claims rights to the UNIX source code base.
The cornerstone of the SCO vs. everyone else legal debate is its claims to the UNIX source code.
Solaris, AIX, Tru64, and HPUX are commercial examples of UNIX operating systems.
Though the tools you use to manage any version of UNIX or a UNIX-like OS like Linux or xBSD can be very different, they are fundamentally very similar in terms of how you use them; i.e., the command-line interfaces, scripting tools, open source and commercial tool support, databases, Web servers, etc. Commercial UNIX variants like Solaris are considered more robust than Linux, but that tends toward more of a religious debate. In other words, it is usually possible to get anything that will run in Linux to run in Solaris or HPUX or AIX or whatever.
Linux vs. Microsoft
Apples vs. Oranges.
If you like your OSes with a GUI over the top and GUI tools to manage the environment, Windows is probably for you (though there are certainly plenty of GUI or Web-based system administration tools for UNIX/Linux OSes).
Microsoft's selling points are its supposed "ease of use" in small- to medium-sized environments, though I'd argue it's just as complex to implement and maintain Windows in large enterprise environments as any UNIX-type OS is. You still get into hacking and tweaking the OS, scripting, and using a variety of standard tools to manage it. Very few large enterprises use only GUI tools to manage Windows as, just like Linux or UNIX, MS has many very good and useful command-line tools to manage its OSes (often much better and more informative--and sometimes necessary--than their GUI counterparts).
And you can use many popular open source tools like Apache, PHP, and MySQL in Windows.