For songs which have great tightness of the music (by which I mean precision in timing between multiple instruments - sorry if this is the wrong term), I find my closed DT660s reveal this well whereas my semi-open DT880s do not.
It makes me wonder if the effect of having different sounds appearing in different places also has the effect of the perception of the timing of those sounds being different. E.g. say a guitar is strummed at the same time as a snare drum is hit but the soundstage puts the guitar deeper than the snare drum; perhaps I then perceive the snare to be earlier than the guitar.
I'm sure some of you, having read this far, are thinking that the reason I perceive the DT660 to reveal tightness better than the DT880 is just an artifact of closed headphones sounding more "impactful", and so I simply notice the tightness more in the DT660s. Compounding this could be the fact I am yet to buy an amplifier for my 250 ohm DT880s, thus subduing their possible "impact" and making them quite less clearly detailed than the DT660s.
While I am open to the perception of tightness being due entirely to the 660s being more detailed and impactful, I would need some convincing as there is such a difference in tightness that I would find it hard to believe that this is purely a perception afffected by different sounds rather than different timings, so I hope you at least consider the possibility that a bigger soundstage will necessarily imply a lesser tightness.
I'm fascinated to hear everyones thoughts.