The same thing. They both surf the Internet. They both have a LCD. The both supports Intel core 2 duo processor. The both support webcam. They both offers the same thing in a different direction.
Update:
The difference between Windows and Mac comes down to one fundamental difference. It has nothing to do with security, viruses, or stability.
It’s all about browser width and the scroll-bar.
Windows
I took a completely statistically useless poll of 2 Windows people and learned that for the majority of the time they keep their browser full screen. This is something done rather easily in Windows. You just click that button in the top right corner.
OS X
In my experience of OS X and Mac people in general, for the most part, we never make our browser full screen. There are, I think, two reasons.
it’s not that easy to go full screen
you don’t really need to
The Why
For all the considerations of web designers there are still a myriad of resolutions at work on the web. There’s the 800px crowd, the new 1024px crowd, and a ton of folks in between and larger.
This, undoubtedly, will at some point in your browsing day cause you to side-scroll or increase the width of your browser.
The Reasoning
Because it is a simple matter for a OS X user to increase the width of their browser on a case by case basis there is never a need to stretch to full screen. The button that most Windows people assume will expand a window to full screen instead, in OS X, expands or contracts to the documents dimensions. In the case of a browser it expands and contracts to the width of the web page.
In windows, there is no easy way to contract a window view. So, rather than jumping back and forth between window sizes a Windows person would just go full screen and stay there.
The Consequence
As such, the majority of a Windows person’s apps are now out of sight, focusing an individual on the app before them, the browser.
At the same time, an OS X person will have a number of apps peaking out from behind and next to their browser.
The Result
Windows people become task oriented people, doing one thing and then another.
Mac people become multi-task oriented, doing multiple things at once.
This is not a pro or con situation. Windows people end up doing less but doing it nonetheless during their day. Mac folk end up doing lots of things but not always getting any one task completely done.