All fairly meaningless

....... I have yet to talk to anyone who has both and actually READS books (at least one a week) who doesn't prefer a Kindle for READING.
In bed, in the dark, I prefer my itouch Kindle app in landscape

.
Well if nothing else, I think it proves that the iPad is
not too bright for reading, considering you can make it dimmer than the Kindle light when reading at night, and that's only by turning down the backlight, not lowering the software brightness control or using the night mode. It's also far more uniformly lit, and I often found that I would catch sight of the LED bulb on the Kindle which was blinding. (it's not my Kindle any more but I was able to borrow it for the photos)
I forgot to take a photo comparing it when I had the Kindle, but I normally turn the backlight down and invert the sepia theme when reading at night, as I find that more comfortable to read in the dark than the white-on-black night theme:
(settings > general > accessibility > triple-click home: invert colors)
And you have just said yourself that you prefer to use your iPod Touch at night rather than the Kindle, so it's clearly
not a better reading device in all situations.
As I've said many times here, it's better in bright sunlight or outdoors, but otherwise I find it too dull and low contrast to read comfortably, you're always trying to find a bright light to be under, and I definitely don't want that when I'm trying to read at night.
What I will say though, is that while the option is great for people that have vision problems, I don't like reading in portrait on the iPad at all, and as you can see in the photos, a single page in landscape is roughly the same size as the Kindle. That size is just right for books, and you don't need to see two pages at once, so I think the Kindle size is perfect for reading novels. The problem is that it's too small for regular tablet app use in my experience, so I wouldn't recommend any of the iPad alternatives. (unless they're solely for reading books)