The D'Addario Steel strings in the Set packs are also clearly better, giving you more tone, strength and longevity. When comparing to other steel string manufacturers you can actually feel the D'Addario strings by hand and tell that they are somewhat thicker & more robust in construction, which may be due to the Hexagonal Core that is unique to D'Addario strings.
The only way to know for sure is spend the money and do your own tests, but it costs you to do so. For me it was well worth a few hundred dollars to find out for my own ears.
jcc