A trait or character is a feature of an organism. Thus heritable traits are better able to adapt to their environment when compared with other members of their species and will be more likely to survive, reproduce, and pass more of their genes on to the next generation.
The same happens with money. Money has traits that enable it to survive and thrive as a Store of Value (SoV), Medium of Exchange (MoE), and Unit of Account (UoA). Bitcoin is a new species that has vastly superior traits to its predecessors.
Fiat currencies and gold are fairly easy to verify for authenticity. However, despite providing features on their banknotes to prevent counterfeiting, nation-states and their citizens still face the potential to be duped by counterfeit bills. Gold is also not immune from being counterfeited. Bitcoins, on the other hand, can be verified with absolute mathematical certainty.
Gold can be melted down and this is when it becomes indistinguishable from any other ounce. Fiat currencies, on the other hand, are only as fungible as the issuing institutions allow them to be. Large-denomination notes have been treated differently to small ones. Bitcoins are fungible, meaning that every bitcoin, when transmitted, is treated the same on the Bitcoin network. However, a particular bitcoin may become tainted by its use in illicit trade and merchants or exchanges may be compelled not to accept such tainted bitcoins. Despite this, there is no alternative pricing for “tainted Bitcoins” so it remains highly fungible.
Bitcoins are the most portable store of value ever used by man. A single USB stick can contain a billion dollars, easily carried anywhere, transmitted near instantly. Fiat currencies, being fundamentally digital, are also highly portable. However, governments can control the free flow of capital. Cash can be used to avoid capital controls, but then the risk of storage and cost of transportation become significant. Gold, being physical in form and incredibly dense, is by far the least portable. When bullion is transferred between a buyer and a seller it is typically only the title to the gold that is transferred, not the physical bullion itself.
Gold is the king of durability — the vast majority of gold that has ever been mined or minted, including the gold of the Pharaohs, remains today and will for near eternity (it can only be destroyed through nuclear transmutation). Many fiat issuing governments have come and gone over the centuries, and their currencies disappeared with them. It would be folly to consider fiat currencies durable in the long term. Bitcoins may be considered durable so long as the network that secures them remains in place. Given that Bitcoin is still in its infancy, it is too early to draw strong conclusions about its durability.
Bitcoins can be divided down to a hundred millionth of a bitcoin and transmitted at such infinitesimal amounts. Fiat currencies are typically divisible down to pocket change, which has little purchasing power, making fiat divisible enough in practice. Gold, while physically divisible, becomes difficult to use when divided into small enough quantities that it could be useful for lower-value day-to-day trade.