My view is the same regardless of where in the forum it’s posted.
They’re different listening experiences.
IMO they should be treated as different journeys, two separate trees to climb.
However, in terms of value, even £2K+ IEMs just need a phone or DAP to power them (just one aspect to consider).
Conversely, even £2K IEMs can’t provide the soundstage of a Fidelio X2HR.
It’s a game of compromises and there are physical limitation inherent to in ears that cannot be overcome - funnily enough, on-ears share some of those limitations.
IEMs generally bring you closer to the sound and as a result, can more easily reveal a lot of detail. Even my WF-XB700s surprise me sometimes with what I’m hearing in the music that I haven’t heard before when using over ears or even speakers.
There are cans like the BLONs that exist which is crazy value for money - somewhat similar would be the Sundaras and HD6XX in the headphone range that are seen as bargains because they’re resolving above their price category.
In any case, both Headphones and IEMs can get very expensive if you’re trying to approach end game. Ultimately, I would say headphones will give you the better overall experience, though it can be more work and effort. Similarly, speakers and subs provide the best experience but can require a silly amount of work (room treatment, measuring with mics, DSP, placement, cables etc).
So, once you figure out that they do things differently, THAT’S where the preference factor comes in.
If you don’t need a very big sound stage or your cheeks to vibrate in any way, and say mids were your main love, I don’t think anything is going to bring you closer than a decent IEM. Electrostats (headphones, not the IEM driver) have silly resolution and by far have had the best mid performance I’ve ever experienced, but if you can match that texture with an IEM, that plus the closeness would win for me - plus electrostats are expensive and bespoke, again, IEMs, plug them into your phone and they’re already great.
My description is becoming cyclic. They’re physically different, it’s down to preference, both are separate journeys that one has to travel individually to answer the question as to which they prefer and what they see as good/better value.