I see nobody answered your 120 hz question
120 hz is better for moving scenes (especially sports) because 60 hz can be a little jerky. The difference is not as great as the manufacturers would have you believe, but if you plan to watch a lot of sports, I'd go with a set having 120 hz. I watch a lot of football about 8-10 feet from a 47 inch TV, and wish I had at least a 50" one because they've gotten where so many of the shots are wide angle from too far away. My 47" TV is a side lit LED and it has a great picture, but I also have a 32" LCD that gets a great picture. The larger the set, the more you want 1080p. I can tell the difference between 720 and 1080 on a 32" TV. I look for a high contrast ratio, but I also go to the store and let my eyes be the judge - I wouldn't buy one I hadn't seen in person.
YMMV, good luck.