That decision is made by the men with the test gear. They are like the Gods of video. I trust in their priests Annunaki, Bandphan and BMXTRIX (installers) and Jostenmeat (generally smart person with OCD) to pass the holy word down to us mere mortals who seek viewing bliss.
I did actually see a nice LCD. A 52" Sony for $3,500. I paid $1,750 for a 50" Panny. Yeah size matters, but not that much.
I wonder which had a better picture.