I recently got the 48" LED Samsung, and it blows my mind... From my 5 year old 32" Samsung LCD it is like day and night... If the difference in the LED and the UHD is as drastic then I would say go for the UHD, but again, I think for your Pops the Size is going to make more of a difference than the LED/UHD... My Dad wouldnt be able to tell the difference...
