It seems like having a digital out on your digital audio player would be better than an analog line out.

If you happen to have an amplifier with a digital input, yeah.

I don't know that I inherently agree with that. It assumes that the amplifier's DAC is better than the player's, and I don't know that's the case. I don't think we're losing much signal in the cable going from the HU to the amp, so that's probably irrelevant.