Customizability, you can make a lot of choices you wouldn’t be able to make. You can find the perfect laptop except you want a matte display over a glossy display you are SOL and have to keep looking. With the FW, you pick your parts.
Also you are looking at in the short term. Long term, when the screen brakes or something happens, it’s generally going to be easier and potentially cheaper to replace it urself, and when it comes to upgrading, you may only need to replace a piece or two rather than the whole laptop. They’re selling 11th gen i7 boards for like $200 right now, if you had an i5 you can get an upgraded laptop with only $200!
Plus, upgrading my mother board / cpu atm, I am now left with a Desktop in the form of my old board.
I have found that running windows without reboots leads to a lot more issues than Ubuntu (or ideally Ubuntu server). I don’t know if the OS just has memory leaks or what but continuous runtime is just not that great on Windows Desktop