Heavy is better. If you have a 30 inch draw, you will have more than enough speed and kinetic energy should be the main concern, not how fast it gets there. Heavy arrows shoot better, are easier on your bow, less noise, ect. I shoot Easton Axis FMJ in the 340, 11.3 grains per inch. Im just a little dude and my total arrow weigh ends up at about 500 grns. Still very fast at a 25 inch draw. Its all relative.....