There is something to be said for a warmer tonality in an IEM, especially if you're using an mp3 player as source. There is no mp3 player that can compete with a high-end source, so you will want to ease up on ultimate transparency, unless you like hearing artifacts with your music.
Still, when I was in the IEM game, I never found any universal-fit machine that could replicate all parts of the frequency spectrum with ease. The dual drivers - Shure E5, Westone UM2, and so on - all tended to roll off severely in the treble and had a rather bloated bass, while the single-driver models - Shure E4, Ety ER-4P - tended to have a hyped-up treble response that made them very steely and metallic.
So, to me, it wasn't so much a choice for what kind of tonality you wanted, but what parts of the frequency range you wanted to get right. Worrying about tonality and subjective interpretation of the music is for considerably higher-end systems.
Enter customs. The ES2 gets a lot more right than any universal-fit IEM I've tried. It's not perfect, and the highs aren't as extended as they are in a full-size headphone. Still, it's good enough at the basics that you can then start thinking about where you want to take the sound subjectively.
Of course, this was all years ago and I've been out of the game for a while.
If I had the choice, I'd take a warmer tonality with a very fluid sound. Not warm in the UM2/E5c sense since that was just mush, but something akin to a SR-001, but better. Like the SFC++ modded SR-001 with VitQ caps
, the 530s haven't done much for me (still trying them), but I love the UM2 sound, especially with some olives....
