When it comes to non-house ball equipment, there is a rather significant difference. Most bowling companies use what is called a "light weight" core in their equipment for weights under 14lbs. Even though your ball speed will be slower, you'll gradually work up the strength to throw the 14 just as good, if not better, than your 12. The 14 also carries much better, since there is more weight for the ball to push over the pins.
The light weight core in most equipment is not as powerful as the normal core found in the 14-16 pound set. The extra weight coupled with the more powerful core yields much better results.
Hope this helps.
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