I believe the seams on different age levels of balls are different. I believe the balls used in little league have higher seams than the balls used in high school which have higher raised seams than major league balls. This difference in height of the seams might cause the ball to bite more and have more movement.
I am really careful about only using balls that are like the ones used in high school games. I don't know if the seams are different between the different brands of balls - but I try to throw with as many different brands as possible. I throw with Rawlings, Worth, Diamond, and Wilson A1010. I only throw NHSF approved balls since these are the ones I'll be using in games & tournaments. I think each age has its own approved ball -
Look and see if some of the balls are scuffed up a little this might cause more movement. I try to pull out balls that are scuffed up and only use them for long-toss and not my pens or flat ground throwing.