For what it's worth, I really like my Sony PRS 650. When you look at the readers, keep in mind that the new Sonys (350, 650, and 950) have the same Pearl screen as the Kindle 3. The factors become 3G versus size versus touch screen versus format types versus personal opinions about the two companies involved. I think either one of them would be a good reader.
One think that no one talks about before purchase is button placement/ease of turning a page. I average 500-700 page turns per book. If the ergonomics of the reader don't work with your hands/preferred way of holding the reader, reading can become very difficult. My arthritic thumbs never did make peace with the PRS 505...