What is better quality to use, line out or spdif?

I plan on getting an apollo uad interface but i will have 2 analoog inputs left and a spdif

i want to connect my iphone 5 and use imaschine and beatmaker and play music

will spdif sound better than using the line out?

for spdif would it be better to use line out to spdif or usb to spidif

what is better quality?

Line out is analog and is subject to all the nasties that can distort and and ruin sound quality. Spdif and USB on the other hand are digital and less prone to distortion.So, use spdif and USB whenever possible.

Does the the iPhone 6 have S/PDIF/headphone out combo?