Most Yellow decks run a mix to stay unpredictable
It's strong in ETB heavy brews like midrange and blink, sacrifice brews where you can sacrifice to something like Attrition and then come back, Aristocrats where you can trigger Blood Artist for wins, life gain for lifelink shenanigans, Voltron and equipment that invested in equipment infrastructure to and any heavy creature build
However, While Wulfgar costs five mana and only doubles triggers based on its controller's creatures attacking, Isshin costs two less mana whilst also doubling triggers that may care about an opponent's creatures attacking, making Isshin simultaneously more flexible and more efficient of an option

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