Number of the Beast or British Steel?

The Number of the Beast, as it's the best album to have Bruce on vocals in my books (primarily due to Hallowed Be Thy Name). Neither band is a favourite of mine though, and there are at least 4 other Priest albums I'd rank more highly than any Maiden album.
British Steel has some fairly good songs. It's a good album, but a lot of the commercial "classics" on it pale in comparison to the more timeless songs on other Priest records. It does have some really strong tracks too, like Rapid Fire, Breaking the Law, and Steeler, but even then, nothing on it absolutely blows me away.

Number of the Beast on the other hand, while not Maiden's greatest, can at least claim Run to the Hills and Hallowed Be Thy Name, which are very powerful songs, so I'd give this one to Maiden.