Plasma is better for SD due to the way it produces the image(similar to CRT) I think Samsung have slightly better SD scaling than Panasonic, though my GT30 is good with SD. Size is an issue, if you sit too close to a flat screen of any type it will look awful, sitting 8ft from a 42" will be better for SD compared to 8ft from a 50" for example, bigger isnt always better. Its also down to the content you view, upscaled DVD can look very good as can some SD broadcasts, Some broadcasts can look awful, many blame there sets when all the set is doing is showing what its sent.