Although their influence at the time was pretty much thrash bands they redefined Speed Metal and made a milestone classic that has since never been matched (Even though Running Wild may have come fairly close). The perfect mix of traditional influences mixed with a dose of youthful speed and aggression and you have Speed Metal at it's best. All musicians are at the best of their game and Scott Travis adds drumming far better to anything done previous to that point and adds a template of beats that would become used more in the decades to follow.
Screaming For Vengeance would have to be my second favourite, I actually think this and Defenders come quite close but this comes out a little on top. Has a better flow and direction and no "Night Comes Down". Which is a pretty average Priest ballad in my opinion.
Out of the 70's stuff I adore "Sad Wings of Destiny" and "Unleashed in the East" (I've always seen this as a "best of" for the whole 70's era Priest sound with generally better recordings of the song). Maybe it should be added here? I've heard it has enough overdubs to be considered more of a studio album
. "Stained Class" I've always found overrated to be honest, almost to the point of it being the worst 70's era Priest album (only rivaled my "Rocka Rolla"). Neither are bad albums (PRIEST RULE!!!) but both aren't as good as say "Sin After Sin" which I think rules and is underrated as hell.
Order best to worst (Something like this I'm not really sure):
Screaming For Vengeance
Defenders of the Faith
Sad Wings of Destiny
Unleashed in the East
Sin After Sin
Ram It Down
Point of Entry
Hell Bent For Leather
Angel of Retribution