Well, that is a tough questions because advantages are based upon a comparison with something else and I’m not sure what you want to compare UNIX to. Also, there are quite a few flavors of UNIX and each has its own advantages and disadvantages. I’ll start with basics, then.
General UNIX advantages:
<li>UNIX is multi-user, meaning more than one user can be logged into the same machine at once.
</li><li>UNIX offers a variety of security models and a basic privilege model that can help keep your system secure.</li><li> UNIX is modular and this helps one application issue not crash the whole machine.</li><li>UNIX has many open source tools available for it that make it very customizable and flexible</li><li>Everything is a file.</li><li>very mature support of SMP</li><li>Supports large memory amounts</li>
That’s a very small start. If you have a more specific question, please ask.