The original holster linked to appears to be made from suede leather. That's what they mean in their description: "premium center cut steerhide." In fairly short order, it will become soft and very pliable - kind of like the Uncle Mikes nylon holsters. Suede leather is tanned by, in part, chromium salt. The fuzziness of the suede retains moisture and grit for an extended time, thus exposing the metal parts of the gun to harmful elements.
The other holster is made from the top layer of the hide. It's veg tanned and is a much better quality leather (for the most part - depending on who does the tanning) and makes for a higher quality holster.