I didn't find the LCD-2s to be in the same league of SQ with the HD800s, while the LCD-3 are. Imo the LCD-2s get obliterated by the HD800s on any decent downstream, even if they sound so differently. The LCD-3s are euphonic and put up much tougher competition and I prefer the LCD-3s treble to that of the HD800s, as it is detailed and airy enough but never tiring. That said the HD800s have clearly better soundstaging and imaging.
Neither of these headphone is perfect and can be fined tuned to preferences through the rest of the downstream (be it amp/dac matching etc, cables, tubes, what has you).
I agree with this.
However, I'm a treble head I guess, thus I prefer the HD800s treble over the LCD-3s.. The HD800s are pretty darn focused to me, and while I also agree the instruments are larger and take up more space with the LCD-3s. The HD800s instruments have their "own" space with more air around them. Where on the LCD-3s the space of the instruments don't separate as well.