The Registered Master Builders Association is an industry body. The relevant consumer-facing benefit is the Master Build 10-Year Guarantee — an independent guarantee covering loss of deposit, non-completion, structural defects and weathertightness. It is not free for the builder to offer (they pay per project) and it is the closest thing NZ has to a serious independent guarantee for new builds.
The Certified Builders Association of NZ is a different industry body covering Licensed Building Practitioners. Its consumer-facing benefit is the Halo 10-Year Residential Guarantee, which is structurally similar in scope to Master Build's 10-Year Guarantee. Whether your builder belongs to one or the other tells you nothing about quality; whether they've actually paid for the guarantee on your specific project does.
Site Safe NZ is about workplace safety, not build quality or guarantees. A Site Safe membership says the company has been through the relevant safety audits — which matters if you're visiting site, and matters legally to the builder, but isn't a consumer-protection mechanism.
What none of these cover: build-method quality, plan library, fitness for your section, or the personality of the project manager you'll actually be dealing with. Don't use a logo as a replacement for asking specific questions.
Verify currency: every one of these can be checked on the public registry of the issuing body. Type the company name in. If the registry says 'inactive' or 'suspended', that's the answer.