Back in the 1940's, the luthier Albert Augustine and André Segovia were responsibles of the first Nylon string set for the Classical Guitar, before that all the guitar strings were made with animal guts. Since then it's the favorite brand for a lot of classical guitar players.
Augustine has 3 types of trebles:
Classic - medium tension treble set with a lyric, warm and bright sound. Great for Classic and Romantic period music.
Imperial - medium tension treble set with a sweet and round sound. It's the sweetest of all the Augustine treble sets.
Regal - high tension set with bright, powerful and projected sound that conserves all the good qualities of the Nylon strings: sweetnes, warmth and expresiveness. This is the brightest Augustine treble set.
All the Augustine sets have the same basses, just varies by tension (Red are normal tension, Blue are high tension). Why change something that's a good product, excellent quality, low priced and best seller, there's simply no reason to...