It had a similar effect on the people being subject to it. In fact, after reading everything I could on past threads in this subreddit and on Wikipedia, I don't see why the Atlantic Slave Trade isn't also called a genocide. Is it because Africans were seen as one large whole and only a minority of them were enslaved? Would it qualify as a genocide since "a significant part" of West Africans were targeted/affected?
One is an attempt to destroy and subjugate a culture in order to force assimilation and prevent uprising against the dominating culture. The other is economical, dehumanization for profit. The loss of a life in slave trade had no benefits, only a loss of money. In a diaspora, the loss of life is one less threat to the ruling power.
One of the defining attributes of genocide is intent. In the slave the intent of the slave trade was not to destroy in whole or in part any African peoples but rather to make money.
The Armenian genocide on the otherhand want only an attempt to displace but also destroy, at least in part, the Armenian people of the ottoman empire. There is some talk about that not being the initial intent but it's clear from the evidence that it already eventually transitioned into genocide.