The extra HDMI port is a consideration, but also the television has the ability to do InfoLink RSS (News, weather, stocks), as well as a slightly different bezel design. I'm not sure if that's a huge consideration, but I just wanted to put that on the table. Most of the actual specifications remain the same.
I hope that helps, and thanks for considering a Samsung product!
PN50A550 OR PN50A650
Wondering if someone can explain if I should be concerned or care that on the CNET comparison of the above 2 tv's, it doesn't list 1080p as an "Input Video Format" for the PN50A550? What does this mean and how does it affect the performance of the tv? Is the only difference an extra HDMI and maybe a better anti-reflective screen? I need to get a TV today!