I like to add to the "watercooler" discussion...
My whole journey has been fundamentally moved by comparison. Comparison, comparison, comparison, was the motivation to change and upgrade.
Wether it headphones, IEM, cables, amps, or Daps. Being able to not only hear, but to compare the difference was key.
Almost anything will sound impressive today, without any direct comparison.
An example for me, was the Sony WM1Z. I absolutely loved this unit... Its analog flavor. I posted many times in threads.
It wasn't until I did a three way side-by-side comparison with an LP P6, and an ibasso 220Max.
It was then when Sony broke my heart with betrayal..
It deviated, where the other two converged in agreement. I realized that not only was sony adding it's "analog" sound, but it was also "reinterpretating" and for lack of better word, "fabricating" every other aspect the sound, soundstage, and cues.
I realized with disappointment that my lovely sound was not only less technical, but more artificial and further away from the actual performance displayed with the other two totallydifferent Daps (Lesabre& R2R). It was then that I realized the Sony dac was acting more like a sound processor, manipulating beauty out of the music with their software, straying further away from the truth. Beautiful, yes, accurate, no.
It was a disappointing moment to realize that they did this on purpose, and to this day in their new offering, they're still gimping on the volume output.
To put it all in perspective, the differences I mention are actually small, to be noted on mainly in comparisons. I still loved the musicality of the sound. It was just time to move on to more resolving players, with companies that don't have the ideology to gimp thier players performance, which is what history shows of the wm1a&1z.
Anyways, the point is that my main tool for me had become comparison observation based on a reference point.
I used this method on all my own measuring and researching, as I modded headphones and amps as a hobby.
So after experiencing many TOTLs, I have narrow down the three observations about sound that I would propose to show how I view aspects of sound for IEMs:
**Detailed = sensitivity
**Technical (analitical) = less harmonics
**Musicality = more **harmonics (distortions)
**Resolving = speed
So we can have an IEM that's detailed (sensitivity) but still sounds like a cartoon, compared to a TOTL performer that had resolve (speed).
Resolve is probably the strongest aspect to sounding real. Speed. That why the Raal SR1a and Stax sounds TOTL.
They can still have great harmonics and sound real (like planars) with speeeed.
Harmonic distortion has nothing to do with actually being better.
For instance Tube amps can have tons of juicy harmonics and still sound real...
So to me:
1- being analytical/ sterile, doesn't need to be a "necessary component" in any type of gear, weather headphones or DAP or system.
2- details come easy in IEM world, and are confused with performance.
3- realism & musicality going hand in hand, are the real achievements of being TOTL.
So with that, my IEM preference has changed from an all BA unit (U12T) to a multi unit.
It needs to have DD bass and BA mids, & ES top end.
I am already biased to want those "signatures" in my sound.
Distortion aspects, to me are only the addded flavors to the signature of the driver, not any description of resolve or performance.
So as for the IEMs, my observations are that
I found the EXT impressive, and although the soundstage was great, but that top end was too much, giving me an almost "U" shaped presentation.
The Traillie had better sound & beautiful mids with good soundstage. It showed me true TOTL performance.
The Odin was right up there, being smooth and balanced, although missing a bit of that top end air, and having less/closer soundstage.
So in the end ended up with the Indigo. It has the resolution/beauty of the others, with a signature closer to the EXT, without the EXT's excess on either (bass& treble) extremes, while having a similar great soundstage. So it was a preference choice, ticking all the boxes of what I preferred, with a soundstage just as good as any of them.
Going from this point on, both the EXT & the Indigo convinced me that DD bass is the way to go if I ever choose to upgrade, but like others already mentioned in this thread, the technology is basically hitting limits and so most are similarly TOTL level, so we're just picking preference.
In the end, it's personal preference.