Originally Posted by Say Chi Sin Lo
... you can't overlook the following reason:
Dead balls are health hazards on the court.
Originally Posted by Frank Silbermann
I prefer tennis balls that are well-used but still lively. E.g., recently opened, but already used for a couple of sets. They're easier on the arm and actually faster.
How are balls used a few sets easier on the arm? Balls lose bounce/rebound during use. You have to swing harder to get the ball to he same location each successive set.
Further, how are used balls faster? You could argue hairless balls fly faster (plausible as far as aerodynamics) but they don't bounce as well (return energy) so are slower.
Dead balls are not reliable. There will ba a greater variance in play between a handfull of balls that have been pounded for days compared to a new can.