What I mean is that eventually one of the two tools might win an absolute majority of users.

There is significant differentiation between the two.

Copilot Pro is integrated directly into Microsoft products. Sure, you have to pay as much as a ChatGPT Plus subscription, or whatever it's called. But paying for Copilot Pro over ChatGPT would suggest that integration with Microsoft products is more valuable than the more general nature the latter.

This is basically the AI business model at the beginning: they're all trying to differentiate themselves from the competition. They know people are willing to pay $20 for the general version of it, so it's a matter of what other features can be added at little to no cost that would pull a person over from ChatGPT to a more specific use of AI in their life.

Also, between Microsoft and Apple, they're already part of an economic oligarchy.