Linux advocates will say that it is more stable, mores secure and does not require as much beefy hardware to run as Windows.
I say the stability factor is bunk and the security argument is just that, an argument. My theory is that there are more Windows exploits because Windows is the dominate operating system and a bigger target as opposed to "more secure at the core." As far as the resources required to run or the beefiness factor, I give this one to Linux -- Windows is a resource hog.
The disadvantages though are cost and the limited selection of POS applications to choose from (again contributing to the cost). Linux applications tent to fall into two categories: very costly for initial purchase and ongoing support or self serve where you have to do all installation, configuration, and support yourself.
Lastly, Linux vs. Windows "which is better" questions almost always draws out the extreme wing nuts from both sides so be prepared for a slew of responses. Frankly I'm surprised I'm the first (soon to be classified Windows wing nut) to respond.