I've been using the Arista Premium Odorless rapid fixer. It's important to me that my paper fixer doesn't smell, because I have such a small dark-closet. It seems to me that ammonium thiosulfate is ammonium thiosulfate, so one might as well buy the cheapest fixer available. It seems that the only qualities to buy on are price, capacity, and keeping ability. If capacity and keeping ability are better between brands of fixers, the more expensive ones might end up being cheaper in the long run.