As far as I can tell the initial damage from the BroodLord benefits from +flyer attack, while the damage the broodling does benefits from +ground attack. Since the broodlings attack a lot faster than the BroodLord, it seems boosting ground attack will increase the effective damage the BroodLord does?
BroodLord gets +2 damage / 2.5s from flying upgrades, while the broodling gets +1 /0.6455s from ground attacks.
Assuming the broodling attacks once as soon as it lands, and then lives for 0.64s, it will have broken even. If it lives any longer than melee upgrades would be better?
Should I be upgrading ground attack in preference to flyer attack? (IE, ground attack AND flyer carapace) if I am using brood lords?
Best Answer
Definitely upgrade ground melee attack,
Not only does ground melee attack have better dps with a brood lord, it also complements the higher tiered zerg units as well (crack-lings and ultralisks become very common for rebuilding a late-game army after an encounter).
With that being said, if you are planning on going mass mutalisk early in the game, the air upgrades may provide a natural transition into brood lords but make sure you start researching ground attack as you transition. Prioritize ground melee, but don't forget that flyer attack helps as well. Zerg late game should provide you with plenty of resources to get both upgrades when your army is maxed.