Best/neutral sound quality out of a Mac(Book)? And out of a iOS device? (Current models.) Does the headphone jack support digital audio output or not)?

Which is the provides the best sound quality the USB,  Thunderbolt, digital socket or perhaps Mini DisplayPort from the Mac of the Mac? and how does that compare with the output of the iPhone/iPod/iPad?

Please note this is actually two questions in one. I both ask about the output of the Mac(Book)s and iOS devices, respectively. Current models.

[For my question not to sound too subjective, I ask about natural, neutral sound.]

More info: NwAvGuy: Headphone &amp; Amp Impedance (Basically he argues less - near zero - impedance is better.)
I am not an audiophile so I can't answer your subjective quality question (which is better-sounding).  But I can tell you that the headphone jack on your MacBook does include optical audio in a format called mini-TOSLINK, which you will need an adapter to get in a standard TOSLINK.

I have never had an audio quality issue with the standard copper-line devices I've plugged into my MacBook or iPhone or iPod.  My experience with outputting to TOSLINK extends only to sound systems which are a bit more dependant on the quality of the speakers, so I doubt the optical connector would be to blame with that.

If you are working with video, you may want to avoid TOSLINK as it apparently adds a bit of delay, but if you follow your "reduce impedance" rule, TOSLINK is probably the way to go.  Everything here is going to go through some digital stage of encoding, but TOSLINK avoids the wire, reducing radio interference and providing enough bandwidth that you can probably live with whatever or lossless (or near lossless) encoding is done.