Scott was the original singer, who unfortunately died far too young in 1980. The band considered breaking up, but eventually brought in Brian Johnson, and rebounded with the huge Back in Black.
I'm really torn on this one. I think the Bon Scott years were filled with more youthful enthusiasm (and some very funny lyrics). Johnson's arrival seemed to bring about a bigger sound. I really like both singers and it's hard to choose one over the other. But I bet some of you can. So who ya got?