For headphone or headset use, the DG is the better option.
I don't think the DS is enough of a jump, for the average user to notice over a DG.
DS does have DTS Connect, which makes it ideal for use with an AV receiver, but for headphone use, the DG is certainly the better choice.
The DG's headphone amp would be of use if you find you want more volume than the DS can provide.