comparing two REST services to each other

Question

Does anyone have any tips on writing tests that compare two REST services? We are doing this as a form of regression testing.

I was hoping to do something along the

Answer 1

Write Junit to get the response objects from both services. And then do the comparison in Java as you do normally for the objects.

But why do you have to write two services that does the same thing and return same results? Atleast I assume the response objects schema is different between two services.