I bought the NGK set because at the time they were considerably less expensive than the Nissan ones ($15 - $20, IIRC). To be honest, I don't know if they are better or worse, but the construction is slightly different and they look pretty!
I do think the Nissan ones are probably made by NGK, but usually OEM is not the same as what companies offer for aftermarket replacements. All the sets that I saw advertised as high performance or such were just way too expensive. I think truckperformance.com has some now though that come in different colors and are less expensive than soemthing like the HotWires or whatever they are. Here's where I ordered the NGK's from. $55 and free shipping...I don't know if that's better than the price you've found.
N GK Xterra plug wires