Bullet velocity and performance.
The gold dot 147s that performed pretty well from My p320 didn't expand as consistently from my LC9S
As I remember, the earliest generations of 147 gold dots were very hard; I think this was to meet some LE penetration test or something. I have heard tell that they made the bullet softer later on. Speer seems to be able to adjust performance of the gold dots based on end user (usually LEO) needs ..for instance there are two part numbers for 125gr gold dots in the 357 sig. One opens up big and one opens up less but penetrates deeper.
My sense is that HSTs and the other weights of gold dots expand more readily. I know I can't tell the difference between a 124 or 147 HST fired into gel from a G43 vs a G17.
