This question can be answered according to your individual needs. In short, it depends on the room in which you want to use the TV. If your living room or bedroom is rather dark or you can darken it, then you should choose the Samsung RU7100. It doesn’t have to provide enough peak brightness to fight against direct sunlight or daylight. Black also looks much better in dark rooms. For the best experience you should sit directly in front of the TV.
If, on the other hand, your room is very bright and you like watching TV or playing games with several people, the LG UM7500 is the better choice. You don’t need the deepest black and higher brightness as well as a wide viewing angle are much more important.