Which of the hypotheses of the origin of mitochondria do you consider more convincing and why?

I consider the symbiotic or endosymbiotic hypothesis of the origin of mitochondria to be more convincing. She is more like the truth. Yes, and there is a living example of this: the symbiosis between algae and ciliates. Moreover, mitochondria have their own DNA and the ability to form their own proteins. This suggests that this organelle used to be, most likely, a separate cell. And perhaps there was a symbiosis of her with another cell, subsequently, she became part of the cytoplasm, that is, organelle.