Any NGK CR series plug has a resistor, that's what the R signifies. If you don't want a resistor, get the C version instead. IE a C6HSA instead of a CR6HSA, etc.
And dood's on the money, a hotter spark won't get you more power, and in some instances can rob you of power by screwing up the flame front. The only times I know of that you need more spark is if you're fouling plugs (fix the problem rather than amping up the spark) or if you're cranking up the compression, but I don't think any of our motors can generate compression high enough to overwhelm a stock coil/plug cap/plug combo.
Kitaco's Super coil is designed to give a stronger spark due to the increased windings in the coil pack. You have to understand that manufactures can produce an ad with improved performance even if it's just right off idle and makes .02 more hp at 1400 rpm.
I've tested them and found no postive results in anything engine combo that I've done.
Same with aftermarket rev box's.
The spark requirements for a pitbike engine even after they are in the mid 20 hp range do not not need an aftermarket ignition.
If you like the bling factor, go right ahead but any engine builder ( who isn't just trying to sell you parts to up his income factor ) will tell you, they are a waste of money.