Mantle will always outshine Mays for collectors because:
--Mantle played for the premiere team in the sport and spent his entire career in the media capital of the USA; Mays played for the least successful NY team and they left partway through his career for a secondary city.
--Mantle was spectacular, good and bad. Mays was steadier. Mantle was better than Mays at his peak but had a much shorter peak. It's better to burn out than fade away...
--Mantle had a peak era as his team won. Mays did not put together a streak like that until he was already in SF, and they didn't win.
--Context counts. Mays had the bad luck to have his peak streak during the strongest era for pitching, so his raw stats (other than the 1965 totals) didn't look that spectacular even though they were elite in context.
--Mays never had a 1961 Roger Maris teammate. Mantle was fortunate enough to have Maris in 61 and for that year to end up being the last legendary Yankees team.
--WS results head to head: Yankees 2, Giants 0. 1951 and 1962.
--Mantle was handsome and white in an era where few black athletes would be chosen for endorsements not aimed at the black community. His marketability and awareness of Mantle were greater than for Mays.
--Mays was overshadowed towards the end of his career by Aaron's home run chase.
And last but not least, Mantle has a card in the 1952 Topps high series; Mays is in the semis.