1) What are leaves that one is entitled to under labour laws
2) What are leaves that one is entitled to under Contract or Agreed term's of service other then (1)
Now, Generally speaking Comp off is a variant of leave that draw its origin from overtime work or work on leave days. So it has a law supporting it. It's Priority is mandatory. Like section 53 of Factories Act.
Then there are Annual Leaves like for example section 78 of Factories Act. They are also legally supported. But intention of legislation is to first allow Comp Off then Annual wages.
There are no legal backing to casual leaves, legally they are annual leaves. So there priority are less because theyy dar there power from service conditions and not a labor law. So there priority is least.