It's interesting that you post this question as it's the exact dilemma I'm going through.
Prior to Listening Test...my rationale for pitting the two against one another.
- Flexibility/Practicality. It comes with two set cables including one for smartphone. Since iPhone 5s is my primary listening device, the W40 gives me the flexibility to take/make call without the awkward process.
- 4R sound. It's more or less a repackaged 4R (based on a lot of write-up) in a nicer/more streamline body (and new cable-connector)
- Price. It's around $160-170 cheaper than the UM Pro50
- The Pro line including this one is Made in the U.S.A....and that means a lot to me.
- ES5 sound. My understanding is that a lot of circuitry came from the much acclaimed ES5...so you basically get the ES5 sound minus the customisation (which means around 20-30% less?)
- Less Practical. I need spent additional money to buy smartphone cable...on top of...
- Price. At around $700 USD where I live, we are taking CIEM territory here....and this before adding smartphone cable
I'm not the most technical guy so my write-up will not have a lot of jargon. I listen mainly to rock, pop, electronic, dance, R&B, hip-hop.
Admittedly, I was hoping that the W40 will be close enough to the Pro50 to make my decision easier...go for the W40 saving $200++ (probably closer to 250).
Sadly, this is not the case. Maybe it's just me but I think that the Pro50 stood way above the W40.
- Details. Pro50 has gobs of detail. I can clearly hear each instrument and track. In contrast, the W40 seems more muddied.
- Bass. I'm not a bass head as I was many years back. However, the Pro50 has surprisingly full-bodied bass...more than most monitor IEM has the right to be. However, it's never overpowering. Just the right balance.
- Percussion/Cymbal. Astounding! The shop owner had me listen to his percussion centric track, and the way the Pro50 treats cymbal and percussion is just otherworldly. They sounded powerful and natural.
- High. Crystal clear to the point of being nearly painful at times (for the vocal that can hit that high note). But the Pro50 never falters.
- Comfort. For me and my ear shape, Westone is one of the most comfortable universal IEM I'd ever worn. And I think the Pro50 took it to another level of comfort for me. Next best fit to CIEM, IMHO.
- Musicality. All this means that I get more musicality out of the Pro50 than the W40.
- Enjoyment. The bottom-line is that I just enjoy listening and rediscovering the music again when I listen to the Pro50. I sat there testing it out...spending over 45 minutes on the Pro50...completely engrossed...and feeling zero fatigue!
So, it looks like if it comes down to this two, I would have to fork up the extra money. But I know that I'll have zero regret (with perhaps the exception of not saving more money to get the ES5 ;)