This is a
follow-up post with more photos comparing the two best Kindle Paperwhites of three I purchased.
Both have excellent contrast (compared the 3rd Kindle that I'm sending back), but the one on the right is better and has a warmer hue. More obvious in the photo is that the one on the right has more even lighting and is brighter when set to the same levels as the one on the left.
In addition, the one on the left has a slightly misaligned bezel and loose case (clicks when squeezed, as if it wasn't quite glued right).
The quality variations between units are a bit of a let down, but I really like the Kindle Paperwhite (better DPI and UI than previous models).