While Lane #1 balls are available in weights down to 13lb, not all ball companies have the same ball available in both 13 and 14#. Often either the 13# is a different core (Track does this, I believe) or a pancake core like a typical plastic ball with a reactive or particle shell. If you ever don't throw Lane #1, you may have trouble finding a "real" ball.
Also, some shops like Buddies don't make any promises about pin positions and top weights on 13# and lighter balls.
Further, with 13# there may be a tendency to overthrow it, the ball just blows through the breakpoint. With 14# and slightly slower speed, you may have a little more control and accuracy. I'd go with 14# if you're really capable of using it. Since you say you throw 14-16mph with 14# balls, I think you have more than enough strength to use 14#.
SH