I don't think they are competitors nearly as much as one might think. If you draw a Venn diagram of people who are thinking of buying a Playstation and others who are thinking about the Switch, they don't really overlap very much, I think. Both companies have very specific propositions in terms of both hardware and software. Do you need portability or not? Do you want AAA story driven big budget productions that Sony is known for(or used to be until they lost their minds), or do you want your Mario, Zelda and such?
Of course there are some who want everything, and other whose taste in games change as they mature in age, that also happens.