Power supply efficiency is without a doubt the most talked about quality in recent years. It's the percentage of current that actually reaches the PC components. If components use a total of 400W, a system with an 80 percent efficient PSU uses 400 / 0.80 = 500W. The same PC with a 90 percent efficient PSU only draws 400 / 0.90 = 444W. It can potentially make a difference in your energy bill, but also translates to other areas. The wasted capacity is turned into heat. The more efficient the PSU, the cooler it stays, the less cooling you need, which improves the lifespan of the components.
The SilverStone with its Gold certificate is clearly the most efficient with an average of 87.8%. The other SilverStone takes second place with 84.6 percent. The other two PSUs do stay above 80 percent, but can't be called efficient compared to modern standards.