A virtual currency is whatever people want it to mean.
1. Existing or resulting in essence or effect though not in actual fact, form, or name.
2. Existing in the mind, especially as a product of the imagination.
3. Computer Science Created, simulated, or carried on by means of a computer or computer network.
Time may be the only way to judge the comparison of tangibles like gold and silver with intangibles like bitcoin or fiat money. In say 100 years or less, the answer will be known which is better.