whether you go handheld or desktop PC depends on what you plan to play and how often you play “handheld” and “sitting at home”
can I throw in an odd alternative 3rd option. Not the steam deck specifically, but many of the windows gaming handhelds have USB 4 support. with that, they enable the user to use an external GPU if they wanted. So if you wanted a better “docked experience” you can get one later down the line and treat it like some middle ground from having a “desktop” pc and handheld pc on demand. down the line you can choose to upgrade one experience or the other when the time is right if you would like a middle of a choice option.
this option is not very setting friendly though, as youd constnatly have to switch back and forth if you choose this path