Common time over 4/4
 

A question was brought up to me and I didn't have a solid answer to provide, "why do we use 4/4 time signature and Common time? Is there a benefit using one over the other?"

Can anyone shed some light on this? Why do both exist?

4/4 is the same thing as common time. The "common time" name and symbol have been around for centuries, going back to medieval times. Its just two ways of writing the same thing.