Typically, my ideal situation is to throw the same ball all night. Doesn't happen often, but sometimes. That being said, I'll chase oil in as long as I can maintain carry while doing so. For me, it's not always about balling down, but sometimes, getting into a ball with a different shape. Typically something that gets down the lane further and corners a bit better is what the shot calls for...for me.
If I strike with 4 balls in practice I base my decision on 1 of 2 things. 1, I pick which one puts me closest to my "comfort zone" or preferred area on the lane I like to play. The more comfortable I am, the freeer I'll be, and the better I'll roll it. #2...if im equally as comfortable with all 4 of them, I'll pick the one I can miss the most with, simple as that.