This is just a list of my opinions on a few of the multiple OSs (Operating Systems). An OS is what makes a computer run; you can run any OS on any computer (most of the time) so debating which is the best to buy. There is no "best" OS, it comes down to what you need. I will provide a long explanation and an analogy of my opinion (HINT: key word is my opinion).
Max OSX gets a lot of undeserved trash. Firstly it is great for artsy stuff or teaching. Macbook Pros, which run OSX as the default OS are the standard for DJ's, producers, photographers, and musicians.
A common misconception is that there are no viruses for OSX, this is a flat out lie. There may be less but all available OSs are susceptible to malware and viruses. One of the downfalls to it is that it is a little "dumbed down", there is not a whole lot of customization you can do when compared with Windows or Linux.
Analogy: Mac OSX is like having a garden surrounded by a glass wall and all the plants have been chosen and planted. It's up to you not to muck it up.
Windows is also subject to a ton of undeserved trash. Windows is the industry leader, and it knows it.
It has the most programs and quite a few programmers/webmasters like it. Dont be scared though, you dont need to be a genius to use windows, it is as simple as OSX but it does allow room to grow.
Analogy: Windows is like having a garden surrounded by a brick wall and a few plants a pre-selected, but you need to pick the rest, plant them, and water them.
Linux is a great (albeit lesser known) OS. It is a great programming environment, but is also super simple a lot of the time. I say a lot of the time because there are tons of Linux distrobutions (the most popular being "Ubuntu", and yes I realize "distribution" is misspelt, its supposed to be like that) each distro has its own advantages and downfalls so you need to find which one is best suited for you. Linux allows for the most customization, but there are multiple places to go wrong.
Analogy: Linux is like being dropped in the middle of a forest with a shovel.