Jacobs was much better and had numerous advantages. Size, speed, the ability to switch stances, and power of his own. Golovkin's age is relevant on the technical side of things, not really the physical. He used to look more versatile but the GGG who became famous, while still technically sound, was more hittable and had less defensive tools. His biggest problem was merely shelling up and stepping back when flurried. Jacobs exploited this over and over.