yeah an IRK is good if you can really ride, allows the motor to grab revs very quickly, but at the expense of torque, and it's hard to get an IRK-fitted motor to idle properly...
An ORK offers adjustability with your ignition timing, which can curtail any kickback problems with starting, and offers some of the revability of the IRK kit, without the massive torque loss...
ORK is probably the better option to go for... ORK also has a lighting coil, should you ever wish to run lights..