I can't tell the difference between brands either, just between different materials and gauges. But material and gauge make a big difference to me. I'd rather die than use a different set of gauges or a different type of bronze in the windings on my steel strings, and I like the sound of even a cheap classical guitar much better than any steel-string. And while new strings do sound a little better to me for the first week or two, that goes away quickly and then they sound about the same for the next couple of years, so I usually keep them on until one breaks.

And that's another thing. I never saw any difference in durability between different brands of steel strings. The only difference I could see is if one brand had sets with exactly the gauges I wanted. But with nylon strings that's a completely different story. The nylon D string of most brands doesn't last very long, and with some brands the strings soon become impossible to tune. I bought three sets of Martin nylon, and their D strings withered and broke after a month or two. Black Diamond was even worse, a week or so for each D string. The only ones I've found that really last are D'Addario Pro Arte. I've got at least two years on my current set. I've never tried Augustine, but maybe I will some time after seeing them praised in this thread.