This is really hard to say. I mean, obviously it's between Switch and PS5 and both will definitely be above 15m this year.
The easy answer is the PS5 since it's destined to have a very strong year, as stock doesn't seem like it will be an issue going forward.
However, if the Switch has a year that included, say, Zelda, Pikmin, 4, New 2D (or 3D) Mario, New DK and Prime 4 (along with any bundle/value adds that could easily happen) and factoring in the extra MK tracks still arriving and the hype of the Mario movie? Then I think the Switch has a shot. And while it may seem far-fetched for a year like that to occur, remember that Nintendo is going to want its big 2023 games - especially the ones that arrive in the last quarter - to sell throughout 2024 as they ready Switch 2's late 2024/2025 launch.
Furthermore, I think that PS5 will have its peak next year. These consoles are going to be around for at least 8 years (PS4 peaked in its 4th year). Closer to GTA6's debut and after there's more software available for the masses to jump in is when I think PS5's biggest numbers will happen.
So for now, I'll stick to Nintendo knowing what it's doing upping production and vote for a slim victory for Switch.