I think this is one of the better matchups so far. While AC/DC is easily more famous and had more success, SMB has made a lasting impression as well. Neither of these bands are giants like the Stones, Beatles, and such, but each has the potential to win again should they advance another round.
All that said, AC/DC just has a closer place in my heart. They never sold out to making the ballads and stuck to their rock jams which are just fantastic. They survived the loss of a great lead singer, and an entire continent's single best contribution to music.