These two are the latest model just released last month:

http://www.amazon.com/gp/product/B002MWYUFU?ie=UTF8&tag=more_info-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B002MWYUFU

http://www.amazon.com/gp/product/B002MWWMH8?ie=UTF8&tag=more_info-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B002MWWMH8

The first one is better and just a hundred dollars more expensive. So just choose the first one if you can afford the money.

However, I do think the Amazon Kindle is better as compared to Sony. You can read here:

http://www.amazon.com/gp/redirect.html?ie=UTF8&location=http%3A%2F%2Fwww.amazon.com%2Freview%2FR266PE1Q47CYNH%3Fie%3DUTF8%26ASIN%3DB00154JDAI%26nodeID%3D%26ref%255F%3Dcm%255Fcr%255Fpr%255Fcmt&tag=more_info-20&linkCode=ur2&camp=1789&creative=390957

I own the Kindle 2 and I like it very much. It is better than Sony Reader because Amazon provide good content support, and the number of books available in Kindle format is kept on increasing (right now there are over 350,000 Kindle books). Sony Reader, however, many users complain that it is difficult to find suitable books, and books on it are more expensive than the Kindle. Other benefits of the Kindle over Sony Reader include the free wireless internet access, and the text-to-speech function.

If you need to read PDF with charts and graphics, you may want to go for the Kindle DX. Read this review and you should be able to decide which one to get:

http://www.amazon.com/gp/redirect.html?ie=UTF8&location=http%3A%2F%2Fwww.amazon.com%2Freview%2FR23V08M2LNB81I%3Fie%3DUTF8%26ASIN%3DB0015TCML0%26nodeID%3D%26ref%255F%3Dcm%255Fcr%255Fpr%255Fcmt&tag=more_info-20&linkCode=ur2&camp=1789&creative=390957

Hope this helps.