The more expensive e-reader, at $249 (Cdn.) is the Sony PRS-600. Weighing in at 10.1 ounces and measuring 6.9 x 4.8 x .4 inches, it's a bit smaller and a bit heavier than the Kobo, and since it's a higher-end reader, it also boasts a few extra bells and whistles.
For starters, it has a touch screen, allowing readers to turn pages with a swipe of a finger. In practice, I found pressing the forward button just as easy, but the touch screen also allows note-taking and handwritten annotation of documents using the stylus sheathed in the top corner. For those whose writing is less than legible, Sony offers a virtual keyboard as well.
Controls are more subtle than the Kobo's - there's a simple row of narrow silver buttons across the lower bezel that control forward and backward movement through menus and books, a home button, a zoom button and an options button. Since this reader also plays music (MP3 and AAC formats), there's a volume control and headphone jack beside the micro-USB connection on the bottom. And since it's a Sony, it supports Memory Stick Duo as well as SD cards for memory expansion. Just as well - it only has about 380 MB of internal memory.
Charging is via USB, as with the Kobo, or using an optional a/c adapter. Battery life is rated at 7,500 page turns, or two weeks.
The Sony supports ePub and PDF formats (and handles PDFs very well), as well as BBeB, Microsoft Word, RTF and text. Adobe DRM handles copy protection here too. There's a built-in Oxford American English dictionary.
Like Kobo, Sony provides desktop software to help manage the reader's library and to download from its online store. And also like Kobo, it looks like a USB drive to the computer, so moving documents around can be as simple as drag and drop.
Either reader can handle basic document display, though Kobo doesn't do as good a job on some PDFs. Both are easy to use, but because of its lighter weight and rubberized back, the Kobo feels a bit better in the hand.
If annotation and note-taking are requirements, the Sony has the edge; it has a lot more functionality - but it's also twice the cost.
(Clarification: In an earlier version of this story, Plastic Logic's QUE reader was described as having an 8.5 x 11 inch display. Those dimensions refer to the body of the device, not the display. The QUE screen will be 10.7 inches diagonally.)