Not sure I buy that. They're one of only two options in operating system but one of many in hardware models. They're much less able to win regulatory capture being a far less regulated industry and in a consumer market.
You could argue I'm just saying they're high quality, which may be true, but the software has been degrading and I have no options if I value openness _and_ quality.
I can flip it and mention features that Apple products don't have that I like.
But this isn't actually an argument for monopoly. That just an argument that you like a company more then the other.