I saw a commercial the other day in which a dog is gargling at the bathroom sink. I didn’t get anything else from the commercial, but it set me to thinking. So this morning, during my customary gargle, I tried to detect an advantage over a simple but thorough swish. The Listerine (Vanilla Mint. Less intense, equally effective) covered about the same area with both methods.
So I come to you, the Cream of the Intellectual Crop, for the answer.
BTW; this question is not about the effectiveness of mouthwash in general.
Peace,
mangeorge
A breeding ground for less than fresh breath is at the very back of your tongue. Gargling, I would guess, cleans this area better than swishing.
possibly gross:If you want a demostration of this, feel the very back of your tongue then smell your finger. Unless you’ve been gargling or brushing your tongue, you’ll get a pretty nasty smell.
I just brush my tongue when I brush my teeth for the same effect.
I brush my tongue too. Learned that in the Navy. 
In 1964. I hurt.
From the horse’s, uh, mouth;
Hmmm. No commitment there.