How about this for an answer: IT DEPENDS! and maybe 'enjoy the choice'.
If you aren't staying particularly long, hooking up the hose is one less thing to do. Also, if things get a little cold at night, your hose can freeze while your tank probably will not. On a recent trip- we were worried about a water leak. Filling the water tank and working the on-off switch was a pretty convenient way to address the situation. Dittos that sometimes campground water might have a 'local flavor'...again, the choice to 'carry your own' is just that- a nice choice.