all due respect to Jeff, I have to disagree. A PSA 1 will typically bring anywhere from 10-15% of what the card books for raw in NM, in the case of the '52 topps Mantle a PSA 1 is gonna go in the $3k range (actually seen a few go right around there and they looked like someone had crumpled it up and played office basketball with it.)
If you look at the value histories of the two, the '52 Mantle has seen significant 'growth' in terms of its value where the '51 Bowman has remained more stable. So from a purely investment standpoint with hope of future appreciation of value, I'd probably go with the '52. However, as a true collector its a crapshoot because both have their own 'mystique'
Just my two cents
