The interfaces for X-Windows and the Macintosh might have many similiarities, but the differences are far more abundant. While both interfaces give multiple windows, which have title bars, scroll bars and close buttons, it is what's contained in these windows that demonstrates the differences between the two interfaces.
While the standard Mac window contains direct representations of files and directories available for manipulation by the user, the X-window contains a terminal by which the user can use the standard UNIX command line interface. However, there are UNIX programs on X-Windows that contain the standard Mac-like pull-down menus. The X-Windows are also different in that you can at any time, iconify the window, which means that you can remove the window from full view, but place an icon representing the window at the bottom of the screen. This option is not available with the Mac, but incidentally is available with Microsoft Windows. Another difference is that with the Mac, you always deal directly with the directories on the hard drive. With X-Windows, you can only deal with the directories through the UNIX command line shell, in a way that is more reminiscent of MS-DOS or PC-DOS. Another interface related similiarity is the fact that both Mac windows and X-windows can be moved, resized, and removed from the screen at any time.
The only real similarities between the two are strictly cosmetic. When you get right down to it, you are really using two totally different operating systems. The point of X-Windows is simply to give the user a graphical interface to use to interact with UNIX, rather than by the old standard command line shell.