In the story of fighting for throne, we have already read about the battle between Trilokavijaya and Yamantaka. Now let us look in more detail about the oath and the corresponding effects in the perspective of tantric practices.
According to ‘Commentry To Maha Virocana Sutra’ (大日经疏), Trilokavijaya means the subjugation of 3 poisons commonly known as: greed (贪), anger (憎) and ignorance (痴). It is due to our past greed that we are where we are at this life; and our greed of this life shall be carried forward to our next life. Hence, the practice of Trilokavijaya is mainly to overcome deva-mara (天魔/deva).
On the other hand, the oath of Yamantaka is mainly to overpower manusa-mara (人魔/human); hence, in the fighting for throne, it best to use Yamantaka ritual to take care of human beings as the power of Yamantaka is much more against the Trilokavijaya according to the individual oath. Having said so, there is one shortcoming about Yamantaka especially when a practitioner also performs fire puja for Yamantaka. This shortcoming is that this practitioner will harness an extremely wrathful and yet hatred heart that will inadvertently causes many living creatures to lose their lives:
In the first phase, kids and dependents of the person will die.
In the second phase, his close ones, master/boss, husband or wife shall die.
In the third phase, all of his enemies or the ones he hate shall die.
So, according the religious perspective, in order to subdue human beings, then Yamantaka is more effective that the Trilokavijaya.
I was once a practitioner of Yamantaka Tantra. Well, true as mentioned above, at the beginning of the Yamantak practice, I would accidentally killed chickens, ducks, snakes etc; until some of the innocent people also be harmed and even dead. Finally, I had to drop the practice of Yamantaka to avoid harming others. Hence, I would like to advice all inspired to practise Yamantaka rituals to exercise caution, and he/she should understand the oath of his/her own Satyadevata. Or this person shall be sorry fairly soon.
It is certainly true that very few people would practice Yamantaka Tantra now days, but we will never know. No one will tell you these types of experiences, not even your own guru Rinpoche.