If you want to (legally) play Nintendo games, obviously buy a Switch 2. You don't have any other option. If Nintendo games aren't that important to you, and/or if you already have a large Steam library, a Steam Deck is a great option.
Personally, I love my Steam Deck, but I'm looking forward to a Steam Deck 2, or maybe a third party handheld, running SteamOS, that has a nice, big, 1080p screen, better controls, and better battery life. More power would be nice, but not if it comes with a louder fan and poor battery life. Honestly, I'd even be ok if the device was focused on local streaming, from my PC.