Gotta look at typing then. Zapdos has a greater # of resistances with its 6 vs Raikou's 3. Granted this also means Zapdos has 2 type disadvantages. (Rock and Ice, which Raikou would also match poorly against as they would resist Electric)
Ie, Raikou and Zapdos worst matchups are going to be the same (presuming rock and ground types can often share moves from the other), with the addition that zapdos is going to take more damage from Ice.
Looking at it from another way, if Zapdo's weaknesses are Rock and Ice, while Raikou's is Ground...Using the Gym Defense Meta, If a non water target is your concern. then consider Snorlax. Snorlax could have EQ. You'd rather have Zapdos. Facing a Dragonite, neither one wins out in typing, but with the same Bulk, Raikou has ample Defense Stat to go toe to toe with Dragonite.
So with the same stamina, and more defense, Raikou pushes out further than Zapdos imo when neither of them would have the type advantage, when the higher attack stat of Zapdos has less of an impact.
Raikou's ideal moveset, Thunder shock / Wild Charge makes up for its lower attack by being objectively better than Zapdo's (charge beam / Thunder bolt)
Raikou is still the better Generalist in this meta.