We have basicly everything you play games on, so also both of these. But the Steam Deck is absolutely the gigachad, even moreso than my actual gaming pc if you just look at hours used.
If you forced me to get rid of all my devices but one, it'd probably be the Steam Deck that'll be left. And yes this consideration included my gaming pc and smartphone.
The only regret I have about buying the Steam Deck is being so late to the party, having acquired it but 6 months ago.