The following table compares the performance of most of the popular lossless compressors. These include WaveArc, WaveZip, and Perfect Clarity Audio, and a few others.
Efficiency tries to evaluate the trade-off between speed and compression.
If you wait a long time but don't get good compression, that's poor efficiency. If it goes super fast, but you don't get hardly any compression, that's bad efficiency too. The idea is to try to strike a good balance between speed and compression.