GUI and UX are not the same. Prusa has pretty good print quality too but not as good a GUI as the Bambu.
UX would include the ability to easily tear down a hot end, replace a nozzle, tighten any belts, and anything else that would affect your ability to print high quality prints.
For prusa, since that's the printer I have experience with the most. Replacing the nozzle and clearing filament jams are pretty easy. But tearing down the hot end to remove debris wrapped around the extruder gear was not.
