I read a review where they said that some of the Samsung panels were outsourced and significantly lower their performance. Here is the post from Amazon:

This information is strictly for prospective buyers who want a Samsung set with a Samsung panel. Samsung is increasing the amount of inferior panels out of Taiwan. These include panels from AUO and Innolux. Samsung also uses Sharp panels in their 60" sizes but this year the UN60J6300 has a AUO panel. AUO and Innolux panels will give you lower contrast ratios, poorer black levels and degraded motion handling. I know because I have last years UN65H6350 which has the exact panel as this years 65" size. I also did a side by side comparison with the 55" and the 75". I was fortunate to have several local folks agree to bring their sets over. We fed all three sets with the same blu-ray sources and FIOS TV. The 55" and 75" with the Samsung panels had superior contrast levels and black levels. Motion handling was also much better. There is a real world difference between these panels. Also you can find your panel at panel look and even the specs are different. You can find your version number on the outside of the box or on the back of the set opposite of the inputs. Here is a list of each size, version number and maker: UN32J6300= TD01-Samsung, UN40J6300=TS01-Samsung, UN50J6300=DH01-AUO, UN55J6300=TH01-Samsung, UN60J6300=MS01-AUO, UN65J6300=AH01-AUO, UN75J6300=TH01-Samsung. Stay clear of the 50", 60", and 65". Bump up to the 7 series if you are interested in the 50", 60" and 65" sizes of this model. Again this is for information purposes only. More info on the panel lottery can be found at avsforum.com. With a Samsung panel this set is a great choice. With a outsourced panel, you are getting less picture quality then you are paying for. Also this set has a 60hz panel instead of a 120hz. That is why it only states Motionflow of 120 vs last year's 6350 which had a Motionflow of 240. I verified this on panel look and the panel is native 60hz. A real step back.