As someone who regularly uses their OG Steam Controller with their Deck docked to the TV, it does work better. Having the trackpad does a lot of heavy lifting for non-game apps. Plus the trackpad simulating a trackball is great for FPS games.

My one complaint is that about 50% of the time the controller double-inputs everything. You can fix it by removing the batteries and putting them back it, but it's still annoying.

And a piece of advice for anyone interested, if you want to Watch Youtube videos without ads, Grayjay is available as a Flatpak. Go to desktop mode and search in dolphin/discover. Then you can open Steam (in desktop mode) and add it as a non-steam game. Once that's done, you can open it in game mode.