Well, I wont say too much about the UM3X that I heard at CanJam vs my ES3X till I do a review, except that the ES3X are still fairly well above the performance of the UM3X. Although the UM3X do bridge the gap between the W3 and ES3X, to sound a little better than the W3, the UM3X are still in the middle and don't have the breathtaking goosebumps affect on me like the ES3X.
That being said,
the UM3X with my UM56 tips are now the best universal fit IEM that I have tried, and easily match the performance of the universit fit demo of the UE4Pro customs. What they bring to the table over the W3 is a more present and detailed midrange, with better transparency. And they offer the benefit of being tuned by various ear tips, with good re-sale value and ability to share them due to being a universal. They seem less sensitive to what tip you need to use for the best sound than the W3.
Also, I found out at CanJam that using the UM56 tips on the Westone 3 DEFINITELY brings the W3 closer to the sound of the UM3X, by filling in the midrange presence and midrange detail, and smoothing the highs and the bass. So, with UM56 tips on BOTH the W3 and on the UM3X, the UM3X would rank between the W3 and the ES3X, but closer to the W3 than the ES3X. But this is because the UM56 tips definitely raises the level of performance of the W3 higher, and EVERYONE who owns the W3 should invest in a set of UM56 tips.
After CanJam, I have decided I would rather sell my Sennheiser IE8 to buy an UM3X than to get rid of the W3 which I shall be keeping.