I agree with Dave. While I don't own either, I've played both kinda extensively. AC/DC and MET are pretty awesome games. IMHO, I think they're superior choices when compared to AS and Kiss--but that's my completely subjective opinion. If you really like a certain band though, that's a reasonable factor to consider as well.
Personally, I like MET more from a gameplay experience, and artwork experience, but I'm not a fan of the band. AC/DC is more recognizable to me though, so the choice between the two would be really difficult.