I don't have experience with ESW9, only M50 which are flat with some bass enhancement studio headphones (great for sound monitoring but not for detailed listening). With ATs IEMs, I just reviewed their new IM02 (dual driver, analytical) and IM03 (triple driver, balanced), and they have a lot of emphasis on mids (clarity, definition, brightness, especially with vocals), where IM03 also has a great bass emphasis. I will be honest, W40 and IM03 are two of my favorite IEMs right now, each having their own unique sound signature. But one problem with ATs new IM series is their bulky design. Their IM01/02/03/04 series is similar to W10/20/30/40 with corresponding number of BA drivers, but Westone was able to use the same shell design for either single or quad drivers, while Audio Technica goes up in size with each model where it will be dependent on anatomy of your ear if it's going to fit you. IM02 had a perfect fitment for me, while IM03 is on a borderline. I'm reading some people returning back their IM50 and IM70 because they are too big. Westone W-series has a professional over-ear ergonomics.