Killer established something of a bad rep from back in the day when they were charging ~$280 for a PCI card that was underwhelming for the average enthusiast, hoping they could ensnare enough WoW addicts with their "snake oil".
That being said, it wasn't like the product was terrible and didn't work; it just wasn't reasonable for its targeted demographic and thus a bit dishonest.
But several things have changed since those days:
1. Qualcomm Atheros acquired Bigfoot Networks
2. the chip has been integrated onto the motherboard
3. a lot of the extraneous "snake oil" is no longer included
That being said, from what I've seen is that the Killer branding is still suffering from that initial rep and I have even seen people vehemently recommend against it in favor of Broadcom or even Realtek when the tests I am familiar with suggest that Intel and Killer are definitely the most desirable NICs these days.
My bias would be to favor Intel, as that's what I've had experience with for several years now (ever since ASUS started something of a standard to include it in their upper end motherboards starting with P67 Sandybridge), and it would seem to make sense as Intel appears to have a driver advantage
That being said, since I've been so familiar with Intel, I am also a bit intrigued at the prospect of playing with something new, and would likely welcome a chance at playing with a Killer NIC.