Providing your APU can provide bleed air, I suggest you are in a much better position as you can maintain pressurization, and therefore don't have to descend quite so quickly.
It should also mean you can try to re-start the main engines. Without bleed air, you'd have to rely on windmilling, and this may not be possible in an A320.
I don't know about A320 specifically, but I suspect the APU output is capable of provoiding full electrical power and hydraulics whereas the RAT will only give you enough for emergency systems.