The debate on whether 4K is of any benefit has been discussed previously on several old threads.
With regard to viewing distance for 4K, the general rule of thumb is to sit back 1.5 times the diagonal measurement of your television screen. If you have a 55 inch screen, that would be 6.875 feet. If you have a 70 inch screen as I have, that would be 8.75 feet. If you only have a 20 inch screen the viewing distance would be 2.5 feet.
These recommendations are from SMPTE and THX.
This article describes a blind viewing test in which 49 participants out of 50 correctly identified a 55 inch 4K set from a 1080P set at 9 feet.
http://www.hdtvtest.co.uk/news/4k-re...1312153517.htm
I am sure folks that think 4K is baloney can produce any number of Internet articles to that effect. One thing for sure, one needs a large screen to enjoy 4K, but it does not have to be threatical in size. 70 inches or better will do nicely. I have an average size viewing room and 70 inches fits in well. My 69 year old eyes can see the significant improvement of 4K over HD if the proper native 4K content is viewed and not up scaled 4K.