It’ll depend on how efficient your phone charger is vs your PC PSU. Looking at some charts, it’s a very close battle but generally the phone charger seems to win out. Probably because it’s more optimized for its max power output, whereas the PSU needs to support a wider range of loads.

silentpcreview.com/power-lost-a-better-way-to-com…

electronicdesign.com/…/gan-fulfills-promise-of-ef…