Career slash line
Mantle: .298/.412/.557
Mays: .302/.384/.557
Their ten years prime slash lines:
Mantle: .312/.440/.605
Mays: .318/.409/.605
So basically the same player, although the Mick was better at getting on base (though .384 career is nothing to sneeze at). Mays was a better defender, while Mantle was a great switch hitter. I think you have to give it to Mays because Mantle might have been a tad better in his prime, Mays led the league in OBP at age 40, while Mickey was basically done at 34.