UM3X is not at the same level as IE80 in my opinion. It is overly thick in mids since it has not much treble. Bass is strong but sounds bloated and it does not go very deep. Soundstage is quite small as well since everything is pushed on to your face. I really did not enjoy UM3X single bit. Ergonomics were great, I will give it that.
W4 and IE80 are amazingly similar to my ears. IE80 has more bass and wider soundstage. Mids are neither forward or recessed on both IEMs. Treble is better extended on IE80 but W4 has good extension as well. I think choice comes to how much bass you want. To me, W4 had not enough bass but for most people it will be plenty. W4 has better ergonomics as well.
Thanks, that's very helpful.