Just to confuse you a tad more, Apple products (in general) have very good DACs and amps, comparing to other devices.
So, solely basing this on audio quality, the iPhone.
OR you could get a dedicated audio player, like a Hifiman or even the iPod Classic models (4th gen and earlier). They have great Wolfson DACs, which is much better than most phones/computers/devices pack. (The Hifiman has a Burr-Brown DAC, I think. Still really good.)
Just my 2 cents.