any Brands of sugar better than others?

[essjay]

I ask this crazy question, as a certain brew store told my brother to only use CSR sugar, telling him that cheaper home brand and coles or woolworths own brands etc contain bulking agents, while CSR is nothing but pure sugar. Wondered if anyone knew anything about it, sounds like a bit of a line to me, and if it was true I still cant see a small percent of maybe cornflour or the like making it worth paying a 30% premium on the big name brand stuff... Its all labelled as cane sugar. I found one place suggesting the cheaper ones are all from bundaberg sugar and repackaged. I also read the cheaper ones are a larger granule, dont know what effect that would be when sold by weight anyway.
Anyone shed some light for me?