Lyris is identical on all platforms, so the platform you choose is entirely a matter of what you are most comfortable with.
In general, the more modern, stable and "crash-proof" operating systems (WinNT, Unix, OS/2) are the better choice for running Lyris, since they are able handle simultaneous tasks well.
A general rule of thumb is this: if the machine is able to handle a medium load Web Server, then it will probably work well for running Lyris.