I rarely use either one and have perfectly healthy teeth and gums. I believe in cleaning from the inside rather than the outside. A diet, like one rich in fruits and veggies, that rids the body of toxins and supplies nutrients to your gums and teeth so they can fight off disease all on their own.
Mouth wash is much better in killing bacteria and more effective. Warm salt water is good when you have some bleeding and nice to have cleansing.
We interrupt Mouth Wash vs Warm Salt Water to share philosophy from days of old:
Today is: 18th October (GMT), in history on the 18th of October, 1016 AD the following event happened:
Danes defeat Saxons at Battle of Assandun (Ashingdon)