Difference between legecy and unified logging

Hi All

I know the basic difference between unified and legecy logging like

unified loggine use from netbackup 6.0 onwards

unified logges are process with vxlogview command to make them readable and legecy logs are straight txt file and for unified logs we don't create directory.

But I wants to know the major difference, Why there is two types of logs or any other major difference.