Actually I'd disagree...analogue will cause a worse signal due to an analogue signal rather than a digital one. Digital signals can be restored and are (at a the mid and top end) higher quality with much higher sampling frequency and therefore quality(obviously depends on the headset). Digital signals basically stream 0s and 1s at however many bit they can which means that at 100Hz with a 4bit connection you will get 400 "digits" of sound but with an analogue signal it just sends a voltage and it therefore tends to "linger" with sub £100/150 headsets(I'm from the UK but you can easily check pricing) Look for 20MHz at a maximum output at least (with audio that provides a minimum needed so that no issues arise with the sound transmission at higher pitches) and you should be ok. I know this is late but at least you'll know for your next headset
All speakers a driven by analogue signals. The question is when the signal is converted to analogue and how well it is converted. Discrete PCI and PCIe sound cards are the absolute best at this.
Furthermore, PCM is a lossless digital format, but it's also enormously expensive in terms of storage. Dolby Digital and DTS are both lossy format, so when a Dolby Digital decoder on a digital headset decodes an AC3 bitstream back to PCM, the restored PCM channels are of degraded quality compared to the original.