Personally I find that the 335 has about the same mids as the 334, but the 334 don't have the low end of the 335. So while the 335 could handle slow pops and ballads nearly just as well as the 334, the 334 can't hold a candle to fast beat pop/rock/metal songs as the 335 as it lacks the low end punch. Thus the 334 is boring in comparison when it comes to pop.
I can't handle the bass level on the 335, makes me feels ill after 30 minutes or so on the bassier songs. With my current setup, I found my 334 have more than enough punch, 335 was too much for me. Back when I still had a iBasso D12, the bass line on both are just not where near as good as what I am getting now. The Just Audio uHA-120Dsc aren't really bassy, just plenty of power and control.
In other words, try thoroughly before you buy. Not just the CIEM sample, but also try out combos that you might move into.
Edited by Ra97oR - 5/5/14 at 11:54am