Usually I try to limit the amount of linking I do to outside forums, but I really think
this site will help you out. Tons of talk on this topic.
Generally speaking, the price difference likely has to do with bells and whistles: better HD audio support, on-board ethernet, newer HDMI version support, newer BD Profile version, faster boot-up and load speeds, and other miscellaneous differences.
This thread might give an exacting comparison of the two players.