It depends what you use it for most: movies or games.

- Movies can benefit from S/PDIF because audio is transported without touching it, letting the receiver decode it and assign it. For games and music, it will be stereo (2.0) unless some kind of encoder is used.

- Games benefit from the seperate stereo mini-jack connections, as they allow 5.1 sound to be played correctly over all the speakers.
Movies and music will have the audio decoded on the PC, meaning it is as good as the DAC-quality (and some other factors) on the PC, which is the SupremeFX. I see it as a good option for most people, where you'd need to have very expensive audio hardware to notice a difference.

I personally choose to use the mini-jacks because it allows (real) 5.1 sound in-game and still allows movies to benefit from this as well. My speaker system (Logitech Z-5500) also isn't of a high enough quality to tell the difference in games or movies between digital or analog.