I personally think the Steam Deck is a far better value, but it really just depends on what you're playing.
Already have a healthy library on Steam, and just want to play your games on a handheld? I don't see why not. But if you're looking to play the next Nintendo games, as overpriced (subjectively) as they seem to be (although, I feel it's important to mention that from what I've seen, DK Bananza is $70, rather than $80/90 like Mario Kart World. Still a little egregious, but it's farther away from an entire $100, at least), then a Switch 2 would probably be the better option. It's just about what you're looking to play, really. But me, personally, I'm gonna have to go with a Steam Deck.