I don't own an Odyssey (frontlight or not), and I've never used a Kobo, but I've had a Gen3 and an Orizon, and tried a Sony and a Pocketbook.
My reasons to prefer Bookeen:
- Custom font support (but I've been told recent Kobos have that too).
- Full justification when the book does not specify any alignment.
- Hyphenation and ligature support (I guess other readers with a non-prehistoric Adobe engine will have these too).
- Possibility of disabling status bar, headers, etc. Just give me the text with as narrow margins as possible.
- Folder display in the library (I might also like some other methods, but I definitely want something else than just sorting by author or title).
- Cover thumbnails in the library.
- Quickly highlight words and short text fragments (I use this a lot to mark typos or other problems that I later fix in the computer, probably not that useful for people who just read).
- Can rotate the screen and read in landscape orientation (I guess all modern readers allow this).
- Can use most features (particularly change pages) with a button, without being forced to move my hand from its comfortable resting position to touch the screen with my greasy fingers.
Things I miss:
- Settings for margins and line spacing (again, I've been told recent Kobos have this).
- Follow links in images (this is an Adobe bug, I'm afraid).
- Fit large images in screen, allow zooming into them. This works with the image viewer, but not with images inside an ePub.
- Dictionary (the Odyssey has that, but not the Orizon).
- Manually rotate the screen (I have to enable accelometer, rotate, disable accelerometer).
- A clock, reading progress and battery meter in a small status bar (which can be disabled).
- Customizable stand-by screens, and a useful start screen which can be operated without the touchscreen.