Mandarin is indeed the more useful to learn because it's more universal. Cantonese isn't, just certain geographic areas have large social enclaves and communities that speaks them. It gives the false sense that Cantonese is more common than they really are.
The truth is strictly what the ones in power perceives it to be.
Enjoy any good things, even the little and menial ones, as you will never know what impending distresses could descend upon you in a moment.