so to answer you kingys.
It really depends where you fishing, out on a boat, wharf, rocks ?
Different rigs for different situations mate.
You mentioned throwing out SPs, If you're going to cast all day long than a light rod/rig is the way to go as you'll get exhausted easily if you're using a heavy gear. Lighter line class will also give you further distance as the line diameter is smaller thus giving you less friction.
Squidgie, I guess heavy leader is the way to go on the rocks, you'll probably have to rub some line against the rocks when landing the fish. Clifton kingies are often very fussy, and lighter leader will give you better hookup rates, but then again there are days when they'll just hit anything offered.