I think that both ethical egoism and ethical altruism get filosofically speaking, destroyed and unabled if they are alone by them self in a society. If one exist, the other one must also do so: In order to balance the ethic.
It is like having a 2, to make it balanced, you have to get a -2.
But if the world's society should have only and only one, and I was the person to choose it, I shouldn't choose any of them. This is, because if I choose egoism ethics, then I would be using egoism ethics to choose it. If I choose altruism ethics, then I would be using altruism ethics to choose it. You might think, does this matter at all? Well, yes. Using an ethic to choose that same ethic as the societie's ethic, is completely incorrect, becuase it would be like trying to describe what (for ex.) transportation means, using the word transportation, or any word of the same root.
I couldn't choose any of them using the other one, becuase it is impossible, but in the case that I did, then, I would still be using one of them so I shouldn't. Maybe the only correct way of choosing one of the ethics is using a third type of ethic, but then, we also have problems: 1)you should also consider that new logic as a candidate, 2) you can't use a different ethic to choose an ethinc, everytime you choose an ethic you are using that ethic to choose that ethic becuase each ethic leads you to choose itself.
But, If I would HAVE to choose one of those two ethics, I would choose altruism ethic because my brain's logic tells me that if everybody does things for the rest, then at least the society would survive for a time, until another civilization comes along (it can be from outer space or a new civilization from earth) and it has both ethics (like all civilizations do) that new civilization would get over the altruism one and the altruism one would dissapear. If you choose a society with only egoist ethic, it would live for an even shorter time and would eventually colapse because it would stop being a society and would become an individually living world.
Resuming this, you can't choose any ethic because you use that ethic to choose that ethic, and you can't choose any of them becuase the ethics alone don't work. Those two ethics alone are like comunism in realty. They simply don't work.