No. Downtuning doesn't necessarily mean heavier. Downtuning mostly means giving a certain color (vibe, if you want) to your song. In the case of Slayer, their songs don't sound less heavy at all in E standard.
1. Open: “South of heaven” 2. Tune: “E” 3. Select all 4. Copy; 5. Create new project, open new project; 6. Paste; 7. Drum parts: apply high compression; 8. Save project as: “Enter Sandman”.
A friend of mine HATES tuning down. Probably because he's usually playing a 12 string. Have you ever heard Slayer played on a 12 string? Well... I'm about to. Yeah, he's straight up 440. I don't mind retuning, but it's better not to. Because you don't know where that fingers been. But there should be a law stating that every tune that has been recorded detuned at a half step or more should also have an alternate version of the same song at the same speed playing back at 440hz so the cool kids could jam with it without tuning or detuning their guitars, keyboards, kazoos, accordions, tubas, etc. It would make the world a better place and more than likely end all war.
In recent news "Scientists discover that the world actually exists SOUTH OF HEAVEN". In Oklahoma for example, an incestuous relationship of a mother and her daughter was discovered after they... got married. If that ain't gross enough, look at their images.