There's a certain speed where I'm at my peak. When I slow down and play doom, that's not it. It's quite difficult to have all the instruments playing tight in a doom song. Due to the slower tempo you can really here when a guitar comes in to early, or the bass is late. Speed can cover that up. And as far as writing. Everybody is good at writing different styles. I can write slower emotional stuff much better than faster songs. That's not true for everyone. Also most doom requires a good knowledge of theory. Lots of time changes, tempo changes, key switches. Good doom isn't just pounding out a few power chords. As with every style, there is good and there is bad. Good is never easy in any genre, even nu-metal.