Death's cover of Painkiller is tight as fuck and on point. Biggest improvement compared to the original imo is a drum player who actually stays on the beat and not drag behind it or let it fluctuate as much. Definitely a matter of taste but I think in the context of this song it just works better in Death version. The overall sound serves the song a bit better too. Kick drum is snappier, snare doesn't ring and clutter the sound realestate for the whole day after you hit it once. You can actually hear the hi-hat and the cymbals clearly. Guitar and bass attack is much more precise and because the drums are mixed so much better you can hear the bass notes and guitar more clearly. I also just happen to like Chuck's guitar sound.
When it comes to the vocals, yeah Chuck Schuldiner was no Rob Halford but the screaming technique is not too different from the way Halford actually sings. Chuck hits the notes but with way more grunt (or whatever you wanna call it) and way less vibrato, which again is very much a matter of taste. A skill too for sure but it easily becomes a crutch for a singer. Vibrato for singers is like a whammy bar for a guitarist. Good thing to have if you can use it tastefully. Annoying when you use it in every fucking note for no reason.
I think he did very well keeping the balance of sounding like Death and enough like Judas Priest to keep it respectful. Undoubtedly one of the best cover songs ever made. Idk if I would go as far as to call it better than the original tho. They can co-exist without either being better than the other.
Now that we got that out of the way let me post a cover that is better in every imaginable way compared to the original. Ok prepare your anuses here we go: