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Minor differences
Detect has only 5 PP, whereas Protect has 10.
Growth has both the attack and special attack boosts double in sun, whereas work up does not.
The many Recover equivalents have to do with distribution and not much else. Synthesis, Morning Sun, Moonlight, and Wish function differently.
Teravolt and Turboblaze exist to have a legendary ability that wasn't fucking Pressure, and not much else. Pretty lazy on Gamefreak's part.
Insomnia and Vital Spirit have to do with distribution. Murkrow, for example, would make more sense with Insomnia than with Vital Spirit.