I live in Brazil too and I always dreamed of an e-reader. I never consider kindle an option exactly for the reasons desertgrandma
Recently I bought myself a sony reader prs-700 because I wanted a device that had search amoung its features.
said, the 505 has much better contrast, it is like look to white paper sheet. But I needed the search so I chose the 700 model.
About the diference between the sonys 505 and 700 I would say that the 505 is like to read in a white paper and the screen in the PRC-700 is like recycled paper.