Answer:
ASCII85 is the most efficient coding system – data size increases by just 20%. It has a couple of minor disadvantages. It uses a larger character set, and so it is only compatible with ASCII (unlike Base64, which supports various close relatives of ASCII). It is also slightly more demanding computationally, since it uses division rather than bit shifting. However, these factors are becoming increasingly irrelevant in the context of modern computer systems. The main reason that Base64 continues to be used more than ASCII85 is probably the simple fact that it has been around for longer.
Step-by-step explanation: