You have to be arriving on a CX flight in First Class or be oneworld Emerald on a CX flight to access The Arrival.

Departing, as oneworld Emerald you can access the first class sections of the CX lounges and BA/QF lounge. CX lounges are better by all accounts.

I suggets you run a search in the trip reports forum to read reviews, or take a look at the CX forum