you can get more revs and more speed on a 15 lb ball.
you can control a 15 lb ball easier than a 16 lb ball.
a 16 lb ball will always carry better and hit harder.
Use the heaviest ball with which you feel comfortable throwing 8-15 games at a time.
A 15 lb ball is easier to throw faster on drier lanes to produce more effective backend, better length and more revs and better carry.
a 16 lb ball is easier to throw slower on heavy oil lanes to produce more backened, more revs and betetr carry.
I personally find it easier to throw a 16 lb with a more relaxed, pendulum-like and muscle-free armswing.
I personally find it harder to throw a muscle-free, pendulum-like armswing with a 15 lb ball.
In general, a spare ball, 1 lb lighter than your strike ball will be easier to control, throw straighter or hook as needs be.
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"Just because you can do something does not mean you should do it."