I have a Pocketbook 622 Touch.
It supports a lot of different files. I use it with Calibri on mac and I can download books from my library. mostly they use epub.
there seems to be no dictionary from english to Portuguese but you can get the menues in Portuguese.
Sony is a bigger manufactor so it will be easier to buy a case etc. I had to order one from Hong Kong on ebay.
and unfortunately Pocketbook doesn't support dropbox. i have made two several firmware uppdates after I bought it. have never had any problems with it.