Paranoid. No contest - Bruce, your magnum opus would easily beat both "Heaven and Hell" and "Brave New World", but it doesn't hold a candle to an album that contains "War Pigs" (a candidate for one of the best metal tracks of all time), "Paranoid", "Iron Man", "Electric Funeral", "Planet Caravan", "Hand of Doom", "Fairies Wear Boots" and "Rat Salad". Did I just mention every single track on it? Well, yes, because it's THAT good.
Brave New World. I do think I prefer "The Mob Rules" when it comes to Dio-era Sabbath, but "Heaven and Hell" truly deserves coming this far. However, "Brave New World" was and is such a triumph in my book - it's an album that helped metal and Maiden really explode into the new millenium. And, most importantly, it's simply the album I enjoy more of the two.