Serial Port : Serial communication takes place asynchronously, meaning that no synchronization signal (or clock) is required: the data may be sent at random intervals. In return, the peripheral must be able to distinguish the characters (one character is 8 bits in length) among the succession of bits which is sent. This is why, in this type of transmission, each character is preceded by a START bit and followed by a STOP bit. These control bits, which are needed for serial transmission, waste 20% of the bandwidth (for 10 bits sent, 8 are used to code the character and 2 are used for reception).
Parallel Port : Parallel data transmission involves sending data simultaneously on several channels (wires). The parallel ports on personal computers can be used to send 8 bits (one octet) simultaneously via 8 wires.
It seems that Parallel Ports are superior to Serial Ports as much more data can be sent per second , are there any reasons to choose Serial Ports over Parallel ports assuming you the computer/laptop has both ???