@SoulSyde
Hey, I have been terribly busy and have been away from Head-fi for awhile, but I'd be happy to answer your question. After re-reading my post, I do see how it could cause some confusion. You were right on the nail when you said I was distinguishing between the SM3's "volume" in the high-end and low-end versus the UM3X's clarity in the high-end and low-end. To put it bluntly, the SM3's are brighter but don't resolve as many details as the UM3X's do (with my ears) and the Low-end has more bump but is not as tight or fast as the UM3X's.
What I really found about the UM3X's was that I could "taste" every note, and really relish the little details in both the treble and bass when compared to the SM3's. I would definitely say that the SM3's are more fun, as in, if I just wanted to crank some metal or electronic while I work without really paying attention, I would choose the SM3's, but I bought the UM3X's for my listening times, when I simply sit with my eyes closed and take in every part of the music. To me the SM3 vs UM3X debate is like Mp3 vs Flac debate (respectively).
Just for the sake of this post, this is why I own a set of UM3X's and TF10's. I use the TF10's for those times I simply want a fun and bassy IEM, but the UM3X's are my go-to listening set (which is why I had them custom molded). Also, I found that the Corda Stepdance worked much better with my UM3X's than the Arrow I used to own (2.1G). Mostly the Stepdance opened up the soundstage and had incredible low-end. It really brought the Westones into a new league.
I know I might have over-complicated the situation, but I do hope that I answered your question. Ultimately, either set is well above anything the average consumer buys (or even cares too), in the end, it might just be better to have both, because sometimes the UM3X is just not what you are in the mood for and sometimes (or mostly in my case) it is.
-MG