What do you guys think about using these balls everytime you play....ball machine or human opponents? Why dont people do this? Im asking because ive never hit with them....do theyplay that bad that you want to avoid them at all costs except for the ball machine. Im almost through with a case of ultra -vis slazenger wimbeldons(very good bounce long life and really a little too harsh for me ) are the tretorns as hard or harder then those? please enlighten me!