Depends on which country either is in. Generally, Emperors are more powerful, because they have complete and total control over their subjects. As opposed to Kings, who in modern times, share their power with Prime Ministers, ect.
But, a better answer could be given if you gave a - time period/specific nation -
They actually have an emperor, not a king. Emperor Akihito.
An emperor holds the highest authority among an emperor, a king, and a sultan.
Japan does not have a king or queen, though it does have an emperor. Emperor Akihito is the present incumbant
When the emperor poops in his pants
his job was as an emperor and king.
A monarchy is a form of government headed by a king, queen, or an emperor.
The Emperor Penguin might be called the king since they are the largest penguin but the 2nd largest penguin is the King Penguin.
In 1812 there was no king in France, but an emperor: Napoleon.
King/Emperor Edward the Seventh.
The Emperor Penguin.
peasant or "subject"(the opposite by gender is queen)
Japan doesn't have a king or queen; it has an emperor and empress. The current emperor is Akihito, and his empress is Michiko.