Zip-off pants for me, which seem more versatile.

When I'm hiking in desert environments, there's not an inch of skin showing, because I am a pale and pasty person. So: long pants there.

And long pants as well in buggy environments, or on unmaintained, overgrown trail.

But shorts when I can get away with it, which tends to be quite often on the usually shady and relatively well-maintained AT.