My opinion is - what do you want the new device FOR?
I have a DR800SG and I love it - but, essentially, all I do is read novels on it (ones I own and library books).
I have zero trouble with PDFs re-flowing ('cause all PDFs I generally have are text-only library books). The Irex also easily reads epubs, which is another library (Overdrive) standard and a format in which I put all my personally owned books.
I bought an ereader 'cause they're cool (and very convenient) but I didn't want to spend a fortune on books - so I HAD to have access to the library. I can check out an ebook (PDF or epub), download it with ADE and sideload it to my Irex with a simple click-hold-drag-drop. No muss, no fuss.
The Irex has AWESOME folder management. I can put my books into any folder I want (mine or Irex defaults). I can access the books several ways via the unit. Using the system is easy without the stylus, though I must admit that using the stylus makes navigation easier. I usually use both hands to navigate: one clicks the menu button, the other operates the stylus. You'd be amazed how fast you can get to the next book. Plus, you can delete books from the Irex so you can keep it neat and tidy.
As I said, I feel the Irex is an excellent ereader for reading books. However, you can take notes (and with ... can't remember who ... a mod, you can transfer/read/print the notes from your PC). It has a scribble function for PDF files.
To top it all off - but not trying to start anything - I like the appearance of the Irex better. It's prettier - because I don't like the plastic look of the Kindles, nor do I like having all that space taken up with the keyboard. YMMV.
So, if you want to read a novel/text-based something - get the Irex DR800. The screen is wonderful and large and I don't have to page turn as much.
Good luck with your decision.
Marilyn
P.S. Please note, I don't own a Kindle, so, obviously, I am spouting my own biased opinion here. As your drill sergeant probably told you: "Opinions are like ... noses (

) ... we all have 'em."