There are no differences. You can always substitute one for the other without change in behaviour.

These two are interchangeable:

   func f[T any]() {}
   func f[T interface{}]() {}

and these two are interchangeable:

   func f(x any) {}
   func f(x interface{}) {}

Maybe OP means the difference between using an interface as type parameter constraint and using an interface as a function parameter / variable type.