My assessment of the lounges I've visited:
CNS - Very friendly, very helpful. It's small, but that's not an issue with the hotel size. Big benefit, a nice balcony overlooking Cairns esplanade and Trinity inlet.
BNE - Smallish and can become very overcrowded. Nothing to write home about but does have a small offering all day which some others don't.
HSP - Best view in Oz. Can get crowded, not very friendly, service is ordinary (drinks fridge is miniscule and regularly runs out without being replenished), sometimes gets overcrowded (understandable given the hotel size) and the food offering is the worst of all Hiltons I tried.
SYD - Best food offering in Oz. Agree with the uni cafe comments, but it ranks probably as my favourite lounge simply because of the wide variety of food and the tendered bar.
HSW - Biggest lounge in Oz. Generally acceptable across the board. Nice deck area, resaonable food offering.
I cannot comment on HoTP or ADL as I haven't tried them.
Although my favourite would be SYD as mentioned above, they all suit me. I don't select a city/town to visit based on the lounge offerings. My least favoured lounge is HSP (due to the cough food offering), but the others are all acceptable in my books. As for breakfast....HSW is my favourite with SYD, HSP, CNS all very good. BNE is probably my least favoured breakfast but that's mainly because the coffee is cough and they do regularly run short of things (on time performance is not high on their list).
EDIT: Another benefit of CNS is happy hour is three hours long (5pm - 8pm). I think most of the others are 6pm-8pm with the exception being HSW which from memory is 6pm-8.30pm (please correct me if my memory errs).