It's not like portability is the only factor at play though.
The other big one is the games. You can't play Splatoon 2, Smash Bros Ultimate, or Pokemon Sword/Shield on Playstation 4.
So true. What are the monster franchises outside of Nintendo first party? Monster Hunter and Dragon Quest?
While Nintendo-only monster franchises in Japan are: Splatoon, Mario Kart, Smash, Pokemon, and Animal Crossing. And maybe Mario as well.
And with Dragon Quest finally hitting the Switch and I can only assume being developed with Nintendo's systems first in mind from here on out, the only mega japanese selling franchise they are missing is Monster Hunter. It'll be interesting to see if Switch starts being the target for Monster Hunter or if Capcom sticks with wanting to sacrifice sales to make the most powerful game they can make.