I assume that nobody really knows that , but I would love to have an answer for that question myself. What are you trying to achieve here anyway ? Something cool really or not ? Do tell me cause I am quite lost with all that matters. I would go for Full HD at least.
Answering my own question.... Actually it displays quite well. Using 4x3 format you get dark/gray bars on both sides, of course. Old analog content like MASH or Gunsmoke is decent. More recent digital content looks almost as good as HD if viewed from a reasonable 12 feet. (The reason you'd use SD input is because there isn't a choice for HD.... as in my case.)