The Ruin scream is solid for sure. My opinion is likely colored to some extent by nostalgia, but while the Ruin scream absolutely makes me want to get down, the Angel of Death scream makes me yearn for the pit. Just really hypes me up every time. I've never missed an Angel of Death pit at a Slayer show that I've attended.
They’re both very good. If you like the screams like that, Killadelphia is an amazing album (and Lamb of God’s best, IMO). It is definitely not often that I advocate for a live album, but this one destroys.