I shoot USPSA, and we are constantly looking for the "magic laod" that will make
power factor, be accurate and 100% reliable.
The current wisdom is heavy bullet, light charge of fast powder. I run 147 gr in 9mm,
230 in 45, with Titegroup or N320 powder. Clays is popular in 45.
Steel Challenge shooters tend toward the fast powder with lighter bullets, as they
do not have to make power factor.
In your G19, you can go pretty light with the stock recoil spring, but I usually
run a 15 lb.
PM for some specific loads if you want.