Xbox by miles. They have four amazing games coming in 2021 that I'm excited for.
-Flight Sim
-Psychonauts 2
-Forza Horizon 5
-Halo Infinite
And I'm gonna add Age of Empires IV as it's a first party game on Game Pass, even though not on Xbox.
That's a dynamite lineup right there. Flight Sim is the reason I bought an XSX, but getting FH5 this year is a huge bonus, as that was probably #2 on my hype list.
Nintendo, on the other hand:
-Metroid Dread looked like more of the mediocre Samus Returns kind of game, not developed in-house
-Advance Wars' return was an overpriced remake with iffy art, possibly no online and a full $60 for a one-to-one GBA remake
-BotW 2 looked like more of the same, possibly uses a similar map to the first
-SMT V didn't look all that good / different / new
Nintendo was fine, they just didn't really hit with me. Not really looking forward to anything there yet. Xbox, on the other hand, has me circling my calendar for multiple games.