Part number 577 60 65-04 is a generic replacement blade set, while part number 577 60 65-05 is the original Husqvarna version, often referred to as "Long Life Safety Blades". Both are compatible with the same models of Husqvarna automatic mowers, but the 577 60 65-05 version is certified as genuine Husqvarna and may offer a slightly longer service life depending on conditions of use.
I don't see any difference. These are the original blades, they are neither harder nor thicker nor better. The blades last approx. 1.5 months with a normal lawn, the mower is on the road 3 times a week all day.