I tried 15 lb. and for the last year and went back to 16 lb. last week. My carry is better with 16 lb.
My speed/revs and carry matches up better with the 16 lb but I hang in there with 15 because it's easiler on my 66 year old body shot 718 last week with 15 lb.
What you can comfortably handle should always trump all other considerations when it comes to ball weight. That's why I'm always amused at all these 16 vs 15 vs 14 pound debates. In most cases your body is going to make the decision for you.