Hey donata, totally on page with you on this subject.
I too love both my LCD4s and my Big Zingalis. My Aries Cerat Kassandra DAC sounds incredible through either. If I had to choose, I would say the speakers, just for the fact I can listen and work at the same time. Wearing the LCD4s all day is not really doable, due to the weight, and the fact I tilt my head down to type a lot and they slide forward or can strain the neck. I had a similar situation with my Stax 009s as well, which even though they are 580g instead of 690g still caused a problem if worn all day.
The presentation of the LCD4s (played fairly loud) is probably beyond most speaker rigs below 200K I reckon. And if I ran my Zingalis that high, the room would energise and the neighbours would be threatening to sue me. The bass on a big speaker rig is more physical and maybe more exciting, but on the LCD4 is very close, and the best bass I have ever heard on any HP, well beyond the Stax 009 or 007s in both depth, slam and detailed bass. Plus the mids are superb, so creamy and smooth, so real....
It is only where we come to soundstage that speakers move ahead. I can't see HPs competing with that, unless the panels were angled more toward the ear and further out / away from the ears. All of which would both look ridiculous and impractical as well.
The LCD4s are IMO the best sound I have ever heard to date on any HP except the HE-1. The sound signature (my ideal) of the HE-1 is closer to the LCD4 than the 009, and that is why I jumped onto Planars.