Samsung has standards for it's panels as does Vizio, Sony, Toshiba, LG etc. The panels are made according to those standards. Don't allow anyone to tell you different. The more expensive Samsung, Sony etc. have different standards and panels are made according to those standards, no matter who makes them. In the case of the Samsung 60F5300 all the panels are the same because they are made to Samsung standards. The high ratings of this TV from Amazon, Best Buy, Sears and the Samsung site itself by customers tell the story. Every model of every LCD LED TV made has some that just don't pass the muster, that is a fact of life.
There is a legal reason for this, all the 60F5300 have to be the same as advertised, otherwise it would be fraud because one panel is better than the other for the same product. Considering that I have taught LAW for 30 years, I would say that this is a good reason.