I have both and I really like the Pocketbook better - it was easy to load whichever dictionary I preferred plus the organizational and file capacity of the PB is much greater than the kindle. The kindle is good if your a casual reader, want easy access to Amazon and need the light option for night reading. The PB is good if you have a large library (I have 25000 or so ebooks in four languages - French, German, Russian and Spanish) I can carry them and my dictionaries on one PB with and SDcard and I use Calibre when I buy books from all over the place and then load them to my PB.
The Kindle kinda makes other than Amazon bookstores hard to use unless you load via your home pc. The benefits there are that you can get a new book at any time and I usually wind up giving it to my husband when he wants something new to read as he is a much more casual reader than I am.
As far as the dictionaries, I like the Amazon ones but I was able to load my preferred Collins, Oxford, and Larousse dictionaries with no problems and easy usage while reading.