I believe the Westone 3 remains the consumer audio product, which has a certain, "color," to its sound, to make it, "feel more natural," so it is more musical and less analytical. The UMX3 will be much more flat, and far more neutral in tonality, so it'll be much more analytical, and far less warm and musical. That's my guess for now; won't know 'til it comes out and I get my pair to compare...
-Ed