Very bad news.
Samsung make far superior panels to any of the crap LG produces.
The 2 main instances off the top of my head are the rMBP having retention issues on the LG panel (as well as severe light bleed in my experience), and the 2011 MacBook Airs, in which the LG panel lacked contrast, and had a dimmer panel compared to the Samsung counterpart.
On the other hand, none of this makes any difference to me, as the crappy glass panels Apple uses cause poor screen uniformity in all of their product lines (and no, just because a lot of people don't have a keen eye to be able to spot it, doesnt mean it doesnt exist).
iMacs, dark bar at the bottom of the screen in addition to varying levels of yellowing to different areas of the screen.
iPhone's, different calibration on every phone, in addition to yellowing issues (not as noticeable due to smaller screen size).
iPad, usual yellowing issues, as well as many units appearing to be "pink" in the 3rd gen iPad.
Retina MacBook, from dead pixels (expected given the amount) to yellowing to pink tinting to image retention, as well as the aforementioned light bleeding.
I could go on and on. It doesnt exist with every sample you'll buy from Apple, but unfortunately given how much of a "cool" company they have become with the kids these days, their products are mass produced on such a scale that good quality is hard to come by.
No doubt I'll still incite a response from the die hard Apple worshippers on here, but you can't argue with facts.
Its a shame really, because these screens are beautiful with the glass removed.