Only because of price. Some people may not want to spend $100 for a wireless card when they can get a similar one minus the separate antennas, if for instance their router was in the same room.Why do you like the PCE-AC56 over the 66 Geoff?
Depends what you need for speed. USB 2.0 is only 450Mbps IIRC. They work pretty well, but you would get better performance and range out of a different unit like the ones we mentioned earlier.Would the use of USB wifi be an option? It saved me some time and money. It's pretty stable for my working needs. ~under $15