sedrosken
Florida Man
MP3 or FLAC will probably not make any difference in a phone, the only phone I know of that aspires to have decent sound is the LG G5? with the hifi plug in module.
I have a Nexus 6P with AKG n20 headphones, not really high end, but not the worst either. The sounds are there, but not the timing in the music, and it can't handle even midly dense music at all. Maybe the AKGs just need some time to loosen up, but I suspect that the phone also lacks audiophile qualities.
I do most of my listening on my laptop, which has some kind of generic HD audio output. I think it's Realtek? Either way, I can't tell too much of a difference even on that. Even that much might just be some kind of placebo effect, but FLACs tend to sound a little cleaner and clearer to me. Not enough to make ballooning my collection from 7GB to 20+ worthwhile, though. I listen on my phone just enough that it's a genuine concern I need to take into account when I'm messing with my library.