Barley is also available as 'barley flakes.' I like to mix/match grains for hot cereal, so this makes it into my options. Both grains have benefits for heart and blood sugar.

They are entirely different. Barley (Hordoleum vulgare) is a grain used widely across Europe and the Middle East, as well as being the basis of beer. Barley generally cooks somewhat faster than oats. Oats (Avena sativa) are less common in the southern climes; it has a much larger grain and generally has to be either cut into smaller pieces (steel-cut or pinhead oats) or steamed and rolled flat (rolled oats, old-fashioned oats).

They are two different grains. Barley is commonly used in Middle Eastern cooking but also in European dishes as for example barley soups.Oats are more typical of the northern climates as they are especially hardy. Both of course have to be hulled.