The RS is the prior generaton of Nova motors and the NS is the newer generation.. Like Thunder racer said, the NS line of motors... ie.. RBv12, Top TS3, Nova NS3, Rex RS3 ect. will be much faster then the RS line, but won't last as long... The cranks are larger, but lighter in the NS line as compared to the RS line... A 3 port NS3 is as fast or faster then a 5 port Nova RS motor...
RC_Alan