PB360 is a clear winner here. Better firmware (programming teams), brighter future and far more professional staff. Had I not gotten a deal on my 2nd K2i of $159 new from Amazon I was already going to buy the PB360 earlier this year. For me, the PB360 is the best designed device for portable recreational reading of novels and what not.
The single drawback for my needs in the PB360 is the louder than normal button click sound when using the large buttons. There are a couple vids on the YouTube demonstrating this but from what people have told me, it's not near as loud as it sounds.