Associate or routine?

I have several outdoor lights that I want to have turn on/off whenever a particular light switch is turned on/ off. These lights are outdoors on outbuildings, and seem to be bordering on the range limit of Z-wave (even with some other Z-wave switches within 30-40ft.) Would it be better to set these switches as associated with the controlling switch, or create a routine to turn them on/off when the controlling switch is used ? Would a range extender be useful if the switches are associated ? Or only if they go through the routine on the hub ?