[Koha] Which OS?

I see directions for running Koha on Debian, Ubuntu, MacOSX, and Windows. Which is best? I'm really a mac head and love the form factor of the Mac Mini. Would a 2ghz dual core mini with 2GB of ram be sufficient to handle 50k of patrons, 120k of materials, and 500K of circ for 1 facility? Thats our current load.