Porta pros specifically seem to be a subjective thing, many describe them as a bit muddy, while some like that as an easy listing mode. The KSC 75 though really impressed me, for me they replaced the ath-m50x. Less base (partly because of no clamping pressure, I read, so changeable with a headband). I do have a cheap chinese hifi IEM I do like and would understand if someone preferred that one to the kSC 75, to further complicate things, but I stuck to them.

Also read positive things about the moondrop old fashioned, to mention an alternative to the porta pro in a very close form factor, not the strange ear clips that are the KSC 75.

I'd argue that the additional space should give the form factor an advantage, though sure, being closer to the ear might also be one. And no doubt, given the huge popularity of IEMs the technology must have seen a lot of progress, so I might be wrong.

Fair point. It's a huge field and I have no defensible option there. I was thinking of the wireless Anker IEM and the various older ones that accompanied my phones, even though as mentioned in the other comment I'm aware of higher class (and sometimes even cheap) IEMs that do exist. But still, I wouldn't generalize it like that, I really do like the KSC 75 a lot and think those kind of headphones are too often overlooked despite their quality, which collides with classifying them so low.