Best/neutral sound quality out of a Mac(Book)? And out of a iOS device? (Current models.)
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.