This argument is all a bit silly really.
Some people don't like reading books on an LCD screen. But everyone who likes ebooks would like reading on pearl screens anywhere. Whether or not there is a scientific basis for this preference is irrelevant. Just because something is not proven usually means we dont yet have the science to prove it. LCD screens are pretty difficult to use outside. Even in the car reading is difficult. i read a lot outside, more than just the 3 hours mentioned.
But you need a light to read the kindle in dim light, but not the nook. Kindles don't have any true apps. But you can access the internet for free in most places in the world and it doesn't take 23 clicks. (Exaggeration is a sign that you know you have lost that argument) kindle is black and white, just like a book. Nook colour is great for reading magazines and illustrations. A hacked nook has wonderful apps available.
I think there are enough differences to say they are two different beasts. And realistically that means they serve different purposes. And that neither is better than the other.