I prefer Variations on a Theme to Conference of the Birds, but only barely. To be honest they might as well be a single body of work. It's just that the opening track on Variations on a Theme might be the best song ever. I've been known to play nothing but the 5 songs on those 2 albums, again and again, for days at a time.
I haven't gotten Om's tracks from the splits with Current 93 or Six Organs of Admittance ... I'm looking forward to that.
Oh, and Sleep? The stuff that legends are made of. Come to think of it, I haven't listened to Dopesmoker all the way through in a LONG time. I need to get back on that. Ganjatron, activate!