I play my music REALLY loud. I don't just want to hear it, I want to feel it... in every part of me. I want to experience the music with as many senses as possible. I turn it up when listening to earphones and when listening to on my computer... especially in my car. I have to occasionally remind myself to drive with the music off for a bit just to see if my car isn't making any funny noises I could be missing.
Mostly quiet. Too old for the loud stuff. Don't need the high energy stuff any more. Don't need the loud music to get psyched for a night out partying. Every now and then I still crank it up, but not very often. Even back in the day I never liked music so loud that you had to literally shout in someone's ear to make them hear you. Some concerts were so loud that my ears were ringing for the next week. I have constant ringing in my ears now. Not worth it.
Depends on the style of music. If it's something slow and soft such as "Ambient" then I prefer quiet because it's supposed to be relaxing. If I'm listening to something exciting such as "Electro", "Funk", something like that then I prefer loud because I wanna feel the beat so I can get it on to the music.