I have 2, .45 cartridges, #1 is a 230g, 950 fps @ 461 ft/lb...#2 is a 165g, 1250 fps @ 573 ft/lb. Help me to understand the real difference between the two. Why would I choose #1 vs #2 (or any size in between for that matter) for self defense purposes? I do not really understand the differences...