Those are too names you don't often see available for free. Picking up either one of them carries a bit of a risk, since they're coming back from health problems, and Williams was in a serious slump before missing time. Still, both these guys are terrific when healthy, which they should theoretically be now. I think you simply have to take the risk of picking up one of them for Catalanotto (my choice would be Williams, in spite of his recent struggles). Whether to drop Hidalgo is a tougher question - I like him for this year, but he's started a bit slowly. This is purely a judgment call, but I'd stick with Hidalgo.
First off, though, drop the Little Cat for Dye. You can then decide who to drop for Williams (possibly Dye himself), thereby making sure you at least have Dye if someone else with a higher waiver priority nabs Williams. Good luck!