Thanks again for all the replies.
jehane, I'm looking to buy in Australia because that's where I live but I'm out of the country right now. I got bored and started doing research early.
Yes, I have noticed that most models are much cheaper to import but the exception is the Kobo which is why I am partial to it. It is the only one that isn't at least 10% more expensive than in the US.
A larger reader is not an option, they are just too expensive. I won't frequently be reading PDFs, it's just an option I think I should have. As long as the reader supports zoom and landscape mode, I am okay with it.
ProfCrash, I'm not too worried about the availability of bookstores anymore. I've done some searching and found a couple that sell Adobe DRM, all the major titles I am planning to read are there so that is fine. I can't buy from the Sony bookstore outside of the US/UK.
Bookpossum, I forgot that the Sony has the ability to organise books. I don't think I will need to store so many books on the device so I probably won't need it but I would really like to have it anyway. Thanks for pointing this out.
Thanks for all the information everyone. I think I've made my decision. It's now between the Sony and Kobo and I'll wait till I get to see them in person before I pick one.