Judas Priest v Rainbow - Easy enough choice here, Stained Class is a good album with a lot of great deep cuts, but bar Beyond the Realms of Death it dioesn't have many big hitters for me, I find Exciter corny and I heard Halford's live version of the title track first so the studio version shows it's age when I listen to the album. Rising only has one flaw, the lyric (and only that one line of lyrics) in Do You Close Your Eyes.
Rainbow with the win
Helloween v Judas Priest - I suspect this will probably be the easiest choice in the last 16 for me. Helloween have a somewhat listenable album from a one trick pony genre, whereas my nomination Sad Wings of Destiny invented pretty much most of the tropes of Heavy Metal. Epitaph is shit though. And I mention this every time I post, and I can't impress this enough, you need to get listening to the album in the real, original running order so it finished with a bang-bang-bang of Victim of Changes, The Ripper, Dreamer Deceiver and Deceiver.
Judas Priest with the win