SteamDeck

I don't find it too heavy nor that it puts any strain on my wrists, if you're playing for extended periods it's more comfortable to rest it on your lap like others have said anyway.

As a counterpoint I love the ergonomics of the Deck. My fingers are quite long and with the Switch I always ended up getting the pins and needles in my pinky and ring fingers, that and pain in my palms where the console would sit, all thanks to the Switch's flat design with straight edges (even though they’re slightly rounded).
With the Deck I haven't had that sort of issues at all, not even during longer sessions. It's so well designed in that aspect.