All are different and have their various strengths. Go by preferred sound signature, not "best performance." Read my "
best headphone" article if you haven't yet.
Your point is valid. However, I assess CIEMs from two perspectives:
- preferences;
- technical capabilities.
I used to focus mainly on my preferred sound signature, which of course was changing over time (I started with bassy IEMs, then I moved to analytical Hf3/ER4s and Custom Art Pro210, then I moved to balanced, clear sounding Custom Art Pro330v2 and Cosmic Ears BA4r, now I have natural, organic 5ways). Nowadays I'm focusing more on the technical capabilities, but of course I'm not disregarding the sound signature. Still I can't stand very bright or very dark phones.
By technical capability I mean:
- natural/accurate PRaT (5ways are ideal in this respect. I'm a little bit surprised that you wrote that those Lears have very good PRaT because according to Rin Choi measurements it have very short decay. My perspective is that short decay does not equal natural PRaT. But, maybe the fact that Rin Choi measured universal version of those Lears has something to do about this);
- instrument separation (after owning 2ways, 3ways and 5ways system I think that the number of ways plays a big role in this respect; I believe that the fact that each driver has its own tube influences intrument separation and as a result micro-details);
- resolution;
- bass extension;
- highs extension;
- dynamics;
- clearness of the sounds;
- 3D soundstage, with emphasis on deepness;
- spaciousness.
Balanced type of sound, emotional vocals, transparency, agressive/laid back presentation and soundstage width I throw into "preferences" category.