The Blizzard Armory API will do in a pinch if you’re not at your WoW computer or using the Discord bot, but if you have a choice, use the addon! The Quick Version Additionally, the Blizzard Armory API does not provide as much information as the addon.
It is supposed to update when your character logs out but this isn’t always the case.
The Blizzard Armory API is often out-of-date. The addon always gets up-to-date info about your character since you are running it in-game and it is also able to get more details (items in your bags, unlocked conduits, items available in your weekly chest, etc). The addon is always better than the Blizzard Armory API Why You Should Use the Addon