there's much debate about this all over the net. that's because both methods are an "artificial" harmonic, meaning they aren't a real harmonic. Officially, an artificial harmonic is where you fret a note and with your picking hand you use your index finger to lightly touch the string at another fret (ex. 12 frets above fretted note), while picking with your thumb. Pinch harmonics are where you dig in to the string with your thumb with your picking hand. Most guitar tab books will use these terms as I have described. However, if you say "artificial harmonics," many guitarists would interpret this as how I have described pinch harmonics. So it is best to clarify. :)

If anyone knows of any good examples of artificial harmonics please post artist - song name. I think Satriani has some stuff. For pinch harmonics, anything with Zakk Wylde.