That's interesting, let me put it on a newbie "Wana be a audiophile" perspective , this will be a long topic so forgive me if there's some errors since English isn't my native language and some technical errors because I'm just learning
1-Music source : you can have a lot of music formats but you easily find FLAC is the way to go but you have different kinds of compression and you can have the same music recorded with different resolution and quality so not easy and them you put the MP3 Vs FLAC and you can't hear a single difference maybe just because the FLAC isn't recorded properly or the original recording isn't basically good enough
2- Audio source : that's the easy part , mostly computer , phone , portable player , cd or cassete tape , didn't know people are still using cassete tapes and seams it's actually a good source for HR recordings but that's not certainly the majority
3- Software : lots of software with filters , EQ , different tricks and adjustments , super confusing
4- Analog or Bluetooth: there's no mistake here , analog is the way but apple products are an exception of audio excellence even though they are BT devices and only support AAC , when LDAC it's the audiophile minimum requirement
5-Dac : lot of setups , different devices , different signatures , different powers , portable , not portable , with or without BT ,with and withou EQ with a clear interference how the sound will be presented on the headphone
6-Amplifier : different powers, you can have a super powerful device but you can't use it with a super sensitive IEM and a amplifier with different power can boost or ruin the sound of your headphone
7-Headphone : so consider the previous factors the same headphone is going to sound different for everyone depending the music quality, the DAC, amplifier , software , EQ and them you have the headphones specs , signature , closed , semi open , open , tuned for a particular kind of music or not and finally you get to the most complex device that's the human ear and on this matter you can find a review saying this headphone is horrible and some other guy saying it's the best headphone he heard , so I had many hobbies on my life but this one is certainly the most subjective and sometimes I think people are talking about things no one can hear and it's just a market thing, sorry if I'm wrong , just a newbie pragmatic perspective