[Mike31154]

It really depends on what type of LED you're wiring. Presumably you're talking the standard Cree 3 watt star in which case it would be difficult to solder the larger 16/18 gauge wire to the pad without cooking the LED. If you're using LEDs such as the 10 watt or larger multi chip emitters, larger gauge would be preferred since you're running a higher current. Smaller gauge wire adds resistance & heats up when too much current runs thru it. Look up the term 'ampacity' of wire. You should get some charts showing the maximum current allowable for a given gauge of wire. Compare this to the current required to run the LEDs of your choice & you should have your answer. Within reason, the larger the wire gauge, the better. Less resistive loss per foot & less chance of overheating.