No, I wouldn't because my goal is to exchange paper dollars for gold. Will the graded coin get a higher return when I go to sell it? I don't know; maybe. But as it is now, if for example you pay attention to modern half eagles (aka, $5 commemorative coins from the US mint), there's no noticeable pattern to their difference in selling price. Not that I've charted things, but when I go to buy, I'll get what's cheapest. Sometimes it's a BU version, sometimes it's a proof. Sometimes graded, or ungraded.
Maybe the bullion eagles (unrelated to the actual "eagles", including half eagles) are a distinctly different market.