I printed the tennis ball in PLA + which bounces well and hasn't broke so far. one thing that I'd recommend is to print with a layer hight of 0.16 to 0.12, it makes the balls last longer. but i wouldn't go below this as the balls i printed whit a layer hight of 0.1 and 0.08 made them to less impact resistant (not shore if that is the correct wording) which caused then to break easily.