Maokai: RoA or Abyssal Scepter
I usually build Maokai almost full tank: Cinderhulk, Frozen Heart, Spirit Visage, etc. but sometimes I like buying some damage, and there are ocassions in which Frozen Gauntlet is not enough. Would you recommend me, then, the Rod of Ages or the Abyssal Scepter?
, as it gives you more magic resist and lowers all enemy magic resist around you. This lets you do more damage, as well as any other AP teammates.
on the other hand only gives you health, the AP is selfish, and takes 10 minutes before it's fully charged. It's really only good as a first item.