Smooth, not every house shot plays the same, if you don't need 4 balls then I'm not insisting you carry 4. The house I bowl in has two different lane oiling machines each one can break down and do weird things to the lane.
Some nights I had to start off with a heavy oil ball going across the second arrow out to 5, and by the end of the night I would be in front of the ball return using my dry lane ball, during the rest of the night I would have changed balls 3 times speeds 5 times angle 6 times and release 6 times. Some nights I would stop at the Pro Shop
and pick up a new ball and still have 5 balls in my locker and not have a ball that would work for that place, then the next week I would use the same ball all 3 games.
There is also no reason that your league balls will not work on some of the sport/pba patterns. Most people don't have the cash or desire to keep up a 12 to 20 ball arsenal when an eight ball arsenal with a few release and speed changes will expand your arsenal to match up just as well with less cost.