This famous name is differentiating its 5.1 rig from Creative's and Logitech's by giving it a USB as well as analogue input.

The advantage of USB is that you don't need a 5.1 sound card for six-channel surround sound.

If you already have a decent multichannel sound card installed in your PC - which many of you surely will - using a USB input seems to offer no noticeable advantage in terms of sound quality.