Well, I may be wrong of course, or maybe ES3X just needs better sources to shine, but when plugging both into what I have, I find RE0 more tonally balanced and equally, if not better detailed. RE0 may not reach as deep in the bass, but it has a more naturally sounding bass in my opinion, with more impact. ES3X sounds dry and a bit unnatural by comparison. Also, I find that ES3X really needs help to bring out dynamics in the music. With my Sony walkman, I had to turn the dynamic normalizer on to make them sound sufficiently dynamic for my tastes. RE0 sound more dynamic out of any source. As for SE530, I think it totally blows away ES3X in dynamics.
BTW, that's why I returned my ES3X a few days ago. Luckily, got most of my money back (~92%). Gotta update my sig.