Living in QLD i can only comment on what goes on here.
I have contacts in the fuel industry and know that all DSL, ULP and PULP come from the same place. Each fuel distributor has a depot at Brisbane, Gladstone, Mackay, Townsville, Cairns ie the major ports. This fuel is pumped from a ship into each depot's storage tanks and so is exactly the same fuel. Where this fuel is loaded from is most likely different each time.
The 98 octane fuels are different. This fuel is transported by truck to either a storage tank at the depot, or directly to the service station. Bp Ultimate comes directly from the Brisbane refinery with their octane boosters and other additives already mixed. I'm not certain about how other companys mix their 98 octane fuel.
From what I have heard, BP Ultimate is the preferred fuel as there have been people who have complained of gummed up parts when running on Optimax.
It's up to the person on what type of fuel they run. Personally I would get my car tuned on one type of fuel then stick with that.