For those not planning to continue to the HSC, the SC does matter as that is the only educational certificate you'd have.
But typically, as with most people in the state, if you move on to year 12, the SC has lost almost all it's meaning, and the HSC certificate is more important. Same goes with the University degree.
But yeah, the SC isn't something easy to study for, it's based on general knowledge you gained throughout the course of year's 7 - 10.
So unlike the HSC, you can't 'cram' the night before.