Out of the four, which brand produces headphones with more of a natural sound?
Do you prefer natural sound or fun sound?
Natural is a very subjective term. I had a pair of AKG K702 for a while, and thought the vocals sounded extremely natural. I then started listening to my MS 400, which sounded boomy and unnaturally warm in comparison. After a few hours of listening, I went back to the K702 and they sounded thin and, as many people put it, plasticky.
Psychoacoustics play a very huge role in what you perceive as natural.
Flat != Natural == Truer words were never spoken.
BTW, I have had long term happiness with Sennheiser 565, 580, and 600, as well as Grado 325's. All of those had a clear midrange, decent bass, good highs, smooth overall sound. But of course, there is no substitute for a lot of hard work reading *all* of the posts here
that describe the sound of 'phones that fit your interest.
I will put a vote in for Pioneer. Brands do not make much of a difference. If you want natural try a Sextett. Did I mention Philips and Sony? You can also try a DT48E etcetera...
Audition a bunch of headphones and you might find that 'natural sound/presentation'.