After useing several differnet shafts, I switched to these skinny tapering shafts called Airforce GT's. These arrows fly better than any other shaft I have shot, but!!!!!! They are expensive and they do not hold up. I broke many arrows. I have now switched back to the Arrowdynamic Trad Lites, which when outfitted with the brass insert and the G nock system, I found them to be the most durable shaft. When you pay a lot for a shaft, you want durability and they fly really well also. I do believe that the tapering shaft helps with penetration due to less drag as the arrow passes through. I like the skinny shaft concept, but I found that they just do not hold up as well. Just my 2 cents, but I have spent plenty figuring this out.
Also, I liked the flight and durability of the axis, but not to fond of the HIT insert.