In the end, as with most topics concerning history the answer depends on the topic at hand. This might be aggravating to hear, but attempting to throw in key-words such as functionalism or intentionalism when discussing the Boxer Rebellion or Meji restoration in Japan would seem forced, and frankly unknowledgeable, to most examiners. Unless a historian is specifically known for adhering to one type of view (such as Kershaw, who is primarily a functionalist and first coined Hitler as a 'lazy dictator' ), you shouldn't be too pressed about announcing everyone's affiliations the moment you reference them in an essay. Still, there are a couple of topics where the functionalist-intentionalist debate is extremely active. In IB History, they are Germany and the Third Reich and Stalin's Russia (especially the Yezhovshchina). For the first topic, the debate centers around whether the Holocaust was a long-planned and intentionally curated event, or it unfolded due to circumstance and the will of individual underling (rather than the Fuhrer himself) as the war went along. A similar question often arises of Stalin's purges and his tolerance (and later removal) of Yezhov. It is crucial that you make up your own mind- can individuals influence history regardless of the society around them, or are long- and societal causes the true drivers of history? If you are able to answer that question succinctly, it shouldn't be a problem referencing functionalist, intentionalist, or structuralist arguments in any of your essays.