Where is this sudden claim that Pixel Qi has low contrast coming from? I've been reading it in more than one place seemingly overnight.
Pixel Qi states that their screens have, "...better contrast ratio
and equivalent reflectance typical of the best electrophoretic displays." (emphasis added) (source: http://www.pixelqi.com/products
Here is a photo grabbed from the Pixel Qi website that compares their screen to a Kindle.
I think the Pixel Qi screen looks better than the Kindle. It seems sharper to me. (the photo looks better on their web page sourced above)
I realize that a lot of what a company says about its own product may be hyperbole but I'm willing to give them the benefit of the doubt until there are user
reports to the contrary.
I really don't believe that the Pixel Qi screen will be worse than current readers so the answer to your question, IMO, is definitely Pixel Qi. With companies like Innoversal lined up with a reported US ~$500 it may well be the cheapest of the lot. It should offer, in a tablet form, an excellent e-reader plus an excellent web browsing tool with full color.