Can we just assume he is a responsible father and his kids health is fine and dandy?
Lets also assume cost isn't an issue among the strings.
So that leaves us with his question of which poly is more likely to help his kid win matches?
Wilson BLX 90 - Wilson Pro Overgrip - 13 ounces
Wilson Gut 16 / Luxilon ALU Power Rough 16L 50/48 pounds