What are the differences between 520 and 525 pitch chains and are there any advantages in using either.

Very little difference to be honest. Pitch refers to the effective width of the chain. Narrower so less friction, favoured by racers and track day users. Doubt if you'd notice adifference, I can't.

Ah ok. What pitch is standard on the nc30

NC30 / VFR400's use 525 chains.

ZXR uses 520 chains.

Can probaly save a tiny bit of weight with a 520 but it'd be negligble.. some peopel switch to it when they change sprockets too.