Windows = each program fills up the screen.
OS X = each program uses a portion of the screen.
The Windows way used to be fine in the days of small monitors, but it's very rigid and inflexible. Now that widescreen monitors are widespread, it is a complete waste of space to have a program filling the screen.
Stretch Safari so it fills the screen and it will have two white bars at either side, or the page will distort and look very unattractive. This is the case with widescreen monitors, regardless of whether you're on PC or Mac.
Windows' way of working is more like a flip chart - one page filling the screen at a time. OS is more like laying all the pages out on a big table and you can pick which one you want in front of you at any one time.
It takes a bit of getting used to, but is a more efficient way of working, even though it might feel a bit 'untidy' at first.
Experiment with Expose (setting are in prefs) and you'll see how to display and pick windows as if they were layed out in fron of you.