Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
A desktop is more than just panels and widgets. It's also an ecosystem of applications specially written to use its resources and to fit its concepts of usability. That means that when you weigh GNOME against KDE, you need to consider their applications as much as the desktops themselves.
Not all software categories vary with the desktop, of course. The time is long gone when KOffice and the only partly realized GNOMEOffice vyed with each other for users -- although KOffice is becoming increasingly mature, and GNOMEOffice's AbiWord, and Gnumeric are all going concerns, most people just use LibreOffice.
Similarly, while some KDE users still favor Konqueror, and GNOME ships with Epiphany, neither web browser is widely used compared to Firefox and Chrome.
However, in other areas, GNOME and KDE support rival applications whose differences are more than just a "G" or a "K" at the front of the name. In many cases, the applications that support the desktops are a direct reflection of opposing design philosophies.