I own the Hanlin (same hardware as the Bebook). The only difference I can think of about the Sony and Bebook is that the Sony has 8 grays and the Bebook 4, but I think there aren't many more differences. My girlfriend told me that a job mate has a PRS-505 and apart from the graphics displaying nicer, she said the screens looks the same. She likes the Hanlin better, in fact.
I think both displays are made by the same company, but I'm not sure. Both are Eink Vizplex technology, so if you didn't the screen of the Bebook, the Sony screen isn't going to be that much better for you.
What did you dislike about the Bebook? (or point me to the thread you refer to).