Yup i love them too, but they do have flaws. In comparison, the m9 feels weightless on the hand and on the ear, isolates like an iem should, and the first thing i notice is the treble extension on certain songs which wasn't there before when using the ex1k. Detail, imaging and separation is neck in neck, after that it's just a preference of tonality. On the mids for eg, i prefer how overdriven guitars sound on the ex1k, the crunchiness and how it blends with the bass guitar though it sounds perfectly fine on the m9. For bass, i think we can agree to not use the "for a BA" phrase on the m9 anymore. Depth, punch/thump, detail, it's all there and it doesn't bleed. For treble, i did put on my most sibilance inducing tracks and they passed. Equally revealing with that realistic shimmer but the better extensions gives it an airier feel, and is more forgiving on badly recorded tracks than the ex1k. So smooth.
In conclusion, if the ex is neutral-bright, the m9 is neutral-slightly warm so the last piece of the puzzle is figuring out which soundsig plays better with your songs. I used it with fairly neutral sources with no eq for reference.
Yup, and i spent more time with it than the z1r. I can't vibe with how the z1r feels on my ears though they sound superb as well. I was somehow more impressed with the m9 for some reason at that time. I guess initial bias played in as well. I was expecting to be bored with the m9 and wowed by the z1r. With the m9, you wear it and it disappears, allowing you to just enjoy your songs with no distractions like a peaky treble or lack of bass or whatnot. Fundamentally the ultimate reason why we invest in these things in the first place.