What is advantages for Z visa holder in China ?

Actually, you have 30 days after you get your Z visa to convert it into a Resident Permit. Resident permit are usually good for a year or less. They usually expire at the end of your contract with your employer. The big difference with countries like Canada and NZ is that as a foreigner, you can't settle in China or stay in China for an extend period of time (usually one year renewable) for anything else than work or school. The only advantage you have with a Resident permit (that's what you'll get when you convert your Z Visa and you have to do that within 30 days after you get it) is peace of mind and being able to stay in China for a "long" period of time without having to leave the mainland and back. Also your resident permit is renewable for another year or which ever period if your employer decide to renew your contract or you get another contract with another employer. I hope this clarify a bit.