Signals of any kind, whether it is electrical, optical, or sound, would gradually deteriorate as it travels farther away from the source. In order to make the signal reach further, a certain method must be employed to return the signal to its original strength after it has travelled some distance. Amplification is the simplest way and it basically increases the signal power. Retransmission on the other hand, is a more complex method that takes the input signal, extracts the information, and sends out that information as a new signal.

The main drawback of amplification is its inability to discriminate between what is noise and which is part of the signal. If noise is introduced to the signal, the amplifier would also increase the power of the noise. With retransmission, the system is able to discriminate between the two and carries over the information while leaving the noise behind. For this reason, retransmission is a better suited method for extremely long distances as the noise in amplification can quickly add-up and make the signal incomprehensible at the destination.

Another good aspect of retransmission is its ability to duplicate the signal on multiple lines. If you try to achieve the same by splitting a single signal into two or more, then just amplify it to restore the original strength, the problem with noise is exacerbated even further.

Probably the one bad thing about retransmission is that it introduces a certain amount of delay or lag. Amplifiers often work in real time and it would automatically output the inputted signal, but at a higher power level. With retransmission, the input needs to be analyzed in order to figure out the information that is to be reconstructed on the output. Although the time it takes is very small, it can still be quite significant when added up.

Amplification is very good when the goal is to have a very large signal that is not expected to travel very far. But for digital data systems that covers great distances, it is much better to utilize retransmission to preserve the original information accurately.

Summary:

1. Amplification is simple compared to Retransmission
2. Amplification does not discriminate between signal and noise while Retransmission often does
3. Amplification is commonly on one media while Retransmission  can easily cross medium
4. Amplification is not suitable for very long distances while Retransmission is
5. Amplification is not as good as retransmission in splitting signals
6. Retransmission introduces a little bit of lag while amplification does not