I have a Humax HD box into a TV HDMI, I also have a Sky+ HD box into a TV SCART (same TV). Switching between them there is precious little difference. OK, the SCART is marginally worse, both are obviously HD pictures. Then again, a good SD transmission often produces a better picture than a crap HD one. E.g, if you watch a M&S advert in good SD it's damn good.