I first believe it won't beat PS4 but i later think that is not even a direct competition.
I mean: the switch is like an hybrid console, is not entirely a homeconsole and not entirely a portable, however it has the advantage of being both.
It is more realistic to compare the PS4 with another "full" homeconsole.
Conclusion is: the switch will sell more for a little bit not for being better on sales but for being also a portable. (like 2 consoles in one)