Gaviscon is a foaming agent. It works by covering your stomach contents with foam to prevent reflux.
In addition to the acid-neutralizing ingredients found in most antacids, over-the-counter Gaviscon contains alginic acid and sodium bicarbonate. When taken as directed, GlaxoSmithKline, the drug's manufacturer, states the combination of the alginic acid and bicarbonate will create a a foam barrier which floats on the stomach acid. This barrier may help reduce the number of reflux episodes and may provide longer lasting action against heartburn.
Pepto-Bismol is an antacid, meaning that it buffers excess stomach acid. The precise reason Pepto-Bismol relieves heartburn remains unknown according to the info I have read. One theory holds that the active ingredient in Pepto-Bismol, bismuth subsalicylate, coats the linings of the stomach and esophagus to reduce irritation from acid.
My opinion - try one of the products if you choose to and see how it works for you.
Kindly,
Kitt