In my (and my friend's) experience, KDE has been notoriously unreliable. We faced issues like the wifi icon just disappearing randomly, the time thingy disappearing, etc.
I have been using GNOME for around five years now (I temporarily switched to KDE 2 yrs back and reswitched to GNOME 3 months later). Till now, GNOME has been extremely stable for me. The only issue that I experienced was a memory (although that was fixed in subsequent updates).
Hence, based on this experience, if you're looking for stability, I would highly recommend GNOME. However, if u'r looking for more customization at the cost of less stability, KDE ain't bad.