I really love this band. Probably my favorite metal band ever. What you think of them
Love 'em, especially the first 6 LPs. My favourite metal band after Sabbath.

I've only heard Number of the Beast

, Piece of Mind, and Powerslave. Loved em all! I really find it hard to call Sabbath metal though. They would be above Maiden for me too. But I always associate them more with bands like Led Zeppelin and Cream, rather than Metallica and Iron Maiden.
Sabbath are like the grandfathers of Metal, who admittedly don't have much in common with the later 'classic' Metal bands like Maiden. Sabbath were still on the verge between blues, rock and what would later become metal. They were in-between, doing their own thing and thus paved the way for 'actual' metal. (I'm mainly talking classic Ozzy-era, of course.) It's like that with many genres and their pioneering bands, after all.