To reinforce JSWolf's point, see
A Comparison of format limitations based on The Hobbit. The best map is the PDF version (which seems to have been taken directly from the printed book), and this is a recent ebook with relatively large MOBI images. Old MOBIs all have tiny images, and the LIT version is usually much better. Today, LIT or ePub is the best of the reflowable formats for images.
So my guess is that the Sony 9.7" is going to be an interesting device. For the KDX, it will be possible to buy Adobe Secure PDFs on a PC/Mac and then strip its DRM for use on the Kindle as a DRM-free PDF. This would also give you many more PDF Reader options on your Desktop (Adobe Digital Editions is a very feature-poor PDF Reader). The Sony 9.7" won't need Adobe's DRM removed, and will (presumably) reflow PDFs if you want. I still don't know why the current Sony Readers don't clip the margins of PDFs, and I am assuming that Sony can do better next time.