As someone who doesn't do much bait fishing (and therefore probably not the right person to answer!), I don't imagine it makes much difference to snapper. I've seen them eat everything from dead birds to polystyrene. They even eat my metal and plastic lures occasionally. Just can't see a snapper turning it's nose up at any free meal, they are the scavengers of our ocean. I do think the various baits have different attractant properties, so oily baits like blue mackerel and skipjack tuna will put out a good scent trail. If the snapper can't find your bait, it can't eat it and that may make the difference on the day. 

Mullet from a fish shop as its NZ,gas stationsetc use frozen from aussie and its mush.Burley is the secret.

Frozen bait should be thawed slowly .... like on a plate in the fridge ..... not at the last minute in the microwave .

Ha ha , just picturing the Mrs trying to get liver on a hook.......yeah , wouldnt want to be in the same ocean let alone the same boat 

Thanks all for the advice, looking forward to trying different baits this Spring!