Kindle DX has large screen. And undoubtedly able to show the PDF in full. I imagine it would be same for iPad, since both has almost the same size. And price-wise, I would prefer iPad - which is multi-purpose device.
http://www.sizeasy.com/page/size_com...indle-3-Screen
What make me curious now is the visibility in Kindle 3. I really wish for a screen shot. As you all know, picture speaks for itself....