>> listening to them side by side makes the difference obvious
>No, it doesn't. First, a lot of people like the Beats audio profile.
I'm no audio expert, but I believe I have a good ear and I use decent gear. I would argue that (most, maybe not all) Beats headphones are objectively worse. I don't mean worse in that people who only listen to pop and R&B are going to like them less, but rather worse at reproducing audio.
I think the way you objectively measure something that reproduces sound is by how accurate that reproduction is. Sure, some listeners are going hear the bloated bass and treble and think it sounds better than a quality pair of headphones. But bloated bass makes some music sound horrible. It works for pop, rap, etc... because there isn't much going on musically. I mostly listen to progressive metal, and it just sounds like shit on Beats headphones. The bloated bass makes everything sound muddy, the treble is way to harsh, and the mid-range is drowned out. Guitars live in the mids.
AudioTechnica M50s have a little extra bass and treble, but metal still sounds great on them. The instruments sound clear and separated. It's punchy. I know what people like is subjective, but I would consider the Beats (again, maybe not all beats) I have listened to objectively bad at reproducing music.