The 9260, since it can use a 160 MHz bandwidth on the 5 GHz networks, is an advanced card and has a higher speed capability than the 1535.  You can check the specifications on the cards..  You are using the same wireless network to test, since some cards need the 5 GHz networks to do their best speeds..  If your local network cannot support the 160 MHz Bandwidth it may not be relevant but Killer Wireless folks may be the best to ask.. The Killer 1550 card is equilavent to the 9260 in capability..     
[IMAGE]Original Killer 1535[IMAGE]After install of Intel 9260
Speedtest.net Results: Killer Wireless 1535 vs Intel Wireless 9260