This is not actually accurate.
Unix is the precursor to Linux, and a lot of Linux is built on modified UNIX code. To say UNIX has no GUI is incorrect. Sun Solaris is a UNIX based system that indeed uses a GUI interface. HP-UX is also a Unix system that provides a GUI interface.
UNIX is just as capable as Linux. Linux's syntax and command structure is a bit easier to understand than UNIX. The GUI with Linux (such as KDE, GNOME and XFCE) are nothing but shells that run ON TOP of a command line interface. Every GUI command can be executed via the CLI in both Linux and UNIX.
Comparing Linux to Windows is not a better comparison as they are nothing alike. Linux and UNIX are MUCH closer in relation to each other.
UNIX, BSD and Linux are all very stable and VERY secure. That alone makes them far different than Windows.
Just a FYI.....
Well, more so Linux is a rewrite of the Unix code. OSes like BSD are ports of the actual code. THe command lines are almost identical, for if you know Linux's command line, you can run the command line in SOlaris, OSX, and BSD. Just another FYI.