Why does 'yum' take longer time in redhat than in centos?

I have been using yum in RedHat. Recently, when I used CentOS I found that while executing the same yum command, it is quicker in CentOS.

Why is that so? Both the flavors have the same package management tool, but the time for executing the same command differs.

Does this has anything to do with subcription in RedHat?

Does anyone know the actual reason?