Several reviewers have mentioned this, but for me the biggest benefit is how quiet this thing is! I've tested all the weights and found the 18 oz to be perfect for regular chiselling. You can't tell from the pictures here, but the 12 and 18 oz are the same size, while the 20 and 30 oz have a thicker urethane band around the head, making them taller and heavier. The weight difference between 12/18 and 20/30 is due to the extra metal plugs in the core of the head. For me the extra weight of the 18oz meant it hit harder than the 20oz, with the center of gravity right in the middle of the head where it meets the bit. Again this thing is made in the USA, very high quality and works great but for me the biggest benefit is how quiet it is. I've had a lot of hammers, but this one lets me do my best work while my kids sleep.