bottom line cost/ease of fit /reliability has to be change the injectors.
but will work with a resistor, all this talk of slowing the injector down is pointless as ecu injector timing is largely based around a time issue and that is what the parameters in the ecu are there for to adjust for time i.e injector opening time. the extra time involved with resistors would not be an "extra factor" or anymore time consuming than mapping for injectors without resistors.