Okay, I'll do this myself now as well.
Dio-Sabbath vs. Dio solo?
This is a bit of a tough one for me. I really like "Dehumanizer" but the sheer mass of Dio's incredible solo-albums (Holy Diver, The Last in Line, Strange Highways, etc.) is probably stronger overall.
Ozzy-Sabbath vs. Ozzy solo?
I don't like Ozzy's solo stuff, so I definitely prefer Sabbath.
Best Power Metal album in terms of vocals?
I can't stand most Power Metal vocalists, but the one I could bear the most was the singer on Nocturnal Rites' "Shadowland"
Best overall Black Metal album?
Rotting Christ - Thy Mighty Contract - the best album I've heard so far, not only in BM, but in all of music. "Triarchy of the Lost Lovers" comes close, so does Varathron's "Walpurgisnacht" and Agatus' "Dawn of Martyrdom"
Your opinion on female vocals in metal?
They can be very tasteful. Some are good, some are bad, same with vocalists from any gender.
Favourite Metal-zine/webzine?
Metal-Observer and Bloodchamber are pretty good.