All preferences aside, I'm going to mildly disagree, and go with the 80s version. Is that not when Back n' Black was made....in the early 80s? To me, this is where the argument is won and lost. Don't get me wrong they've made good albums in both decades, and Bon Scott was okay, but whichever decade Back n' Black is in, I'm going for.
If Brian Johnston had died immediately after Back in Black was released then he'd have been thought more highly of than Bon Scott. Back in Black is the greatest AC/DC album ever released. However, since BIB AC/DC have released album after album of AC/DC parodies that they've become a pisstake of themselves and that's such a pity.