45 RPM
The slower a record spins, the more it's sound quality is affected. In order to deliver the best possible sound, the record must spin faster (45 RPM). However, when a record spins faster, the amount of information it can hold is reduced. The desire to improve sound quality, while ensuring adequate playtime, is a problem that still persists today. Obviously, the "convenience" drawback isn't an issue when you're willing to pay more for two 12-inch records instead of just one.
One-Step
To understand what makes "One-Step" so special, let's compare it to the usual process. The lacquer is transformed into a first father stamp with an inverted groove structure. This is then transformed into a mother stamp with the correct groove structure. It is only in the next step that the press stamp used to produce the disc is made. With the One-Step, the lacquer itself is converted directly into a press stamp. The result is a disc that sounds closer to the original master tape.