There are some people's opinions on the pocket pro versus the prs-300 here
https://www.mobileread.com/forums/showthread.php?t=61389
Astak do ship the pocket pro internationally, so no problem there. I'm not sure about the Sony but you can add fonts to the Pocket Pro (there is a thread somewhere here how to do that).
When it comes to availability of books, both devices support DRM-epub format, so your book choices for purchased books is essentially the same. Sony do have an ebookstore but it is not currently available outside the US or UK...besides if they do go international I somehow doubt they will restrict the sale to purely Sony e-readers.