See A Comparison of format limitations based on The Hobbit
. The 1st screenshot is for MOBI (AZW) and the 6th is PDF. In this case, the PDF version would probably work well on the KDX providing one of the two PDF text sizes (portrait or landscape) was ok for you. The MOBI/AZW images probably look better on a KDX than on a PC because they will automatically be doubled to fill the screen, but the PDF images are already full size.
However, unless you are willing to strip DRM from Adobe PDF ebooks, this will be moot for most ebooks on the KDX. You are also giving up the capabilities not supported by PDFs on the KDX.
When full mobile Adobe Digital Editions appears on a device with a 9.7" EInk screen then both PDF and ePub will often be available for the same ebook. At that point readers will have to choose between the two formats, and ADE will also reflow the PDF if you want a bigger font.