The most apparrent comparison I can make is the interest in tone. Perfecting the quality of each note/chord/cluster/sound. Really, this is not tone at all. Timbre, or the quality of a musical note or sound that distinguishes different types of sound production(http://en.wikipedia.org/wiki/Timbre), is what I mean.
Yes, I did just cite Wikipedia. Fuck you.
The composers of those eras of interest, and the downtuned sound most doom bands profess is a sound obsessed with expressing/changing/creating a very specific shape-colored sound. Either by playing a completely unrecognizable cluster of notes that is derived from a completely different musically theoretical way or simply putting fatter strings on your guitar and using very specific amplification parameters, the goal is similar.
And, now, where they both differ is dynamics. In fact, all modern music has completely lost all sense of dynamics whatsoever... We can blame this on the loudness obsession in audio production today and throughout history. Or, we can just say that dynamics are not a marketable aspect of music, and have somehow been pushed out of interest by flooding the (this sickens me as I type it) 'music-market' with over-produced, simple and repetitive ( to the point of insulting) 'songs'.
Here are some examples of all that I have mentioned:
I was going to post some Lady Gaga, because she is a fucking demon from the depths of a plastic sweatshop factory made of chicken nuggets. But, I will spare you the indecency.