Depends entirely on what you play. For most people, a standard gaming PC is going to be your best bet, especially if you play FPS titles, but for a select group of people a Steam Deck makes a ton of sense.

If you play mainly older titles, are on the go frequently, and enjoy a console experience, you can even hook your Deck up to a TV with a docking station, or to a monitor, keyboard, and mouse. It's super convenient, and is like a gaming laptop/console hybrid, almost like a switch with an entire capable Linux install for productivity.

For someone in need of something like that, I think a Deck might make more sense!