Why Hedgehog and Squid do not replace helicopter depth charges

Would Hedgehog or Squid be better helicopter weapons than depth charges?

No; their main benefit is preserving a ship's sonar contact during an ahead-thrown attack, and the systems are not practical helicopter payloads.

Hedgehog and Squid are valuable because a surface escort can attack without first passing over the target and losing sonar contact. That advantage belongs to the ship-and-sonar combination rather than to the projectile alone. Their launchers and ammunition are not practical loads for an early helicopter. A rotary-wing aircraft therefore continues to use depth charges or other compact weapons while exploiting its own ability to hover, reposition, and receive contact information.