DUDE... you got it right. The difference in the 7 and 8 is that the 7 will burn hotter. The 8 is a cooler plug. The higher the # the cooler the plug will burn. The lower the # the hotter the plug will burn. Thats all i know, as for anything else ya might wanna ask one of the smart guys of DRN!
Spark plugs create Radio Frequency Interference (RFI) when they fire. During the days of points and condensors, this wasn't a problem except with your AM radio. Nowdays, you have all kinds of electronic control modules and Capacitive Discharge Ignitions that MAY be suseptable to this interference. Resistor plugs limit the rush of current thru the plug and dampen the RFI generated by the plug. There are several other posts throughout DRN that you can search on this subject and opinions vary. But as an electronics technician, I'd say....if your specifications call for a resistor plug, then use it. You dont know what problems you may cause with your bikes electronic control module by generating un-necessary RFI. AND, you aren't going to see any increase in performance by running a non-resistor plug anyway, so why bother???