Both coins are British and both are bought and sold as bullion. They answer different practical questions: how much fine gold is in the coin, and whether you are buying a modern fine-gold coin or the older 22 carat sovereign.
Fine gold, not total weight
A full sovereign weighs 7.98 grams and is 22 carat (916.7). Its fine gold content is about 7.32 grams. A one-ounce Britannia is a modern fine-gold coin, struck at a higher fineness, with one troy ounce of fine gold. Comparing them by “one coin” without the fine-gold figure will mislead you.
Fractional sovereigns (half, quarter) and fractional Britannias exist. Always read the actual coin in the listing, not the family name.
Bullion value and other value
A common-date bullion sovereign or Britannia is usually discussed against its fine gold plus the dealer’s premium when you buy, or the buying rate when you sell. A proof coin, an unusual year, or a coin in original packaging can be of interest beyond melt. We do not promise a collector price, and we do not treat every sovereign as scrap.