But to be more precise: both "emit" light depending on the ambient light. Of course it's comparable.
The only thing really throwing off the LCD would be the white balance, but with the right sensor that too could be fixed (e.g. a camera with fixed wight balance behind milk-glass).
(E-)Paper reflects blue light, LCD backlight emits it. The only difference is that the color balance and brightness don't change with the sunset on your screen unless you install a tool like flux.
Light is light. Looks the same = probably is the same. Bands are just a bit narrower with LEDs, but I wonder if that makes any difference biologically if it looks the same.
eink/epaper is reflecting ambient light just like every other object in the environment so your vision won't need to adjust when glancing back and forth
If you set your monitor to the same brightness that paper or a non-backlit screen would have in your room, then your vision doesn't have to adjust to the different brightness levels.
Same for TV. Don't watch TV in a dark room!
When I had a modest home theater with a projection TV (the old bulky kind, not a separate projector and screen), one of the best things I did was to light the white wall behind it with a soft neutral gray light.
The technique at the time was to use a small fluorescent desk lamp on a small table behind the TV, with the fluorescent tube wrapped in a specific color of lighting "gel" to make it a neutral gray. The lamp was aimed up at the wall behind the TV. This made everything much easier on the eyes.