As much as I'm a Sabbath fan, Live At Last was dreadful, an earlier recording (poor at that) put out by a previous record label, without the bands knowledge, very poorly pressed too! There were much better bootlegs, such as the Live in Lund concert.
I would think that Judas Priest ' Unleashed in the East' is a better early 'metal' (as opposed to heavy rock!) live album.