And how do you figure? Every review of it shows it beating or equaling intel nics. Not a huge fan of the software so I don't load it but the nic itself and their firmware/drivers seem rather good minus some of the weird problems that seem to crop up with Intel nics and tethering.
It is obvious you have never used a Killer nic card. The limited testing done for reviews doesn't show the weaknesses that show up under constant usage. For example, I often find the Killer software memory usage growing to out of control levels. After about 2 weeks without restarting the machine, you end up at nearly 750MB of ram used for the nic cards. And by that point, the software is simply unusable. The "packet prioritization" is entirely garbage. I tried it a couple times, including over different software versions. In the end, the system was nearly unusable due to buggy software blocking random things from using the internet entirely.
Trust the people who have used recent Killer products; they aren't worth it.