Should i stay in Fremantle or perth city?

Fremantle is a great place. An old sea Port with trendy cafes . My son lives in fremantle he has travelled the World several times he has lived in 3 other Countries and he loves getting back to Fremantle. One of your answers says it will be cheaper but thats not so. Housing is expensive there. I have been to perth many times. My choice would be Fremantle.