Metallica have a huge body of awesome work compiled over many years ... John Mayer, while his releases have been a bit on the light side for my tastes, is still a very good guitarist as evidenced by some of his live stuff.
Given the choice I'd see Metallica for sure, but I don't think John should be written off just yet ... I think he'll surprise as an opener for the Stones.
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Ultimate Rock Music Poll
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