I bring my own pool balls, as the hall I play at has cheap ball sets and they are badly maintained. I've been carrying my own set for years, and they have the scars to show it due to old tables with ball return systems (now they have newer tables with drop pockets), balls flying off the table, etc. They are still better than the club's balls; I have a new set waiting for the old one to get to a state that I'll have to retire them.
They have at the club two sets of Black Aramith, but you need to pay extra to rent them, and they are not that clean, so I prefer to bring my own.
If it's just a night out at the pool hall, I probably won't bring my set of balls.
I also won't bring them to a league or a tournament, as I think that everybody should use the same type of balls, and I don't want to deal with moving the balls from table to table between matches.
At another place that I visited just last week for the first time for a tournament, they have sets of Aramith black for all the tables, and everything is maintained nicely, but it is more expensive to play there, and I prefer my usual club atmosphere better.