The 120Hz panel will refresh the picture faster.
As well, if you have content that is 24Hz, 30Hz or 60hz, all of them equally divide into 120Hz, so there will be no 3:2 pulldown, as there may be with a 24Hz (or film mode) content on a 60Hz - which doesn't divide.
If that's too technical, that's just a fancy way of saying that you'll get a smoother, more-lifelike picture due to a panel that is more compatible to different recording and broadcasting methods. As well, the processing for a 120Hz panel gives you a smoother picture during fast motion.
If we can answer anything else, please let us know how we can help.
Thanks for your interest in Samsung products.
--Mr.Samsung